Haoran Li
Other people with similar names: Haoran Li
Unverified author pages with similar names: Haoran Li
2026
Into the Gray Zone: Domain Contexts Can Blur LLM Safety Boundaries
Ki Sen Hung | Xi Yang | Chang Liu | Haoran Li | Kejiang Chen | Changxuan Fan | Tsun On Kwok | Weiming Zhang | Xiaomeng Li | Yangqiu Song
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Ki Sen Hung | Xi Yang | Chang Liu | Haoran Li | Kejiang Chen | Changxuan Fan | Tsun On Kwok | Weiming Zhang | Xiaomeng Li | Yangqiu Song
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
A central goal of LLM alignment is to balance helpfulness with harmlessness, yet these objectives conflict when the same knowledge serves both legitimate and malicious purposes. This tension is amplified by context-sensitive alignment: we observe that domain-specific contexts (e.g., chemistry) selectively relax defenses for domain-relevant harmful knowledge, while safety-research contexts (e.g., jailbreak studies) trigger broader relaxation spanning all harm categories. To systematically exploit this vulnerability, we propose Jargon, a framework combining safety-research contexts with multi-turn adversarial interactions that achieves attack success rates exceeding 93% across seven frontier models, including GPT-5.2, Claude-4.5, and Gemini-3, substantially outperforming existing methods. Activation space analysis reveals that Jargon queries occupy an intermediate region between benign and harmful inputs, a gray zone where refusal decisions become unreliable. To mitigate this vulnerability, we design a policy-guided safeguard that steers models toward helpful yet harmless responses, and internalize this capability through alignment fine-tuning, reducing attack success rates while preserving helpfulness.
Jailbreaking Large Language Models with Morality Attacks
Ying Su | Zheng Mingen | Weili Diao | Haoran Li
Findings of the Association for Computational Linguistics: ACL 2026
Ying Su | Zheng Mingen | Weili Diao | Haoran Li
Findings of the Association for Computational Linguistics: ACL 2026
Pluralism alignment with AI has the sophisticated and necessary goal of creating AI that can coexist with and serve morally multifaceted humanity. Research towards pluralism alignment has many efforts in enhancing the learning of large language models (LLMs) to accomplish pluralism. Although this is essential, the robustness of LLMs to produce moral content over pluralistic values is still under exploration. Inspired by the astonishing persuasion abilities via jailbreak prompts, we propose to leverage jailbreak attacks to study LLMs’ internal pluralistic values. In detail, we develop a morality dataset with 10.4K instances in two categories: Value Ambiguity and Value Conflict. We further formalize four adversarial attacks with the constructed dataset, to manipulate LLMs’ judgment over the morality questions. We evaluate both the large language models and guardrail models which are typically used in generative systems with flexible user input. Our experiment results show that there is a critical vulnerability of LLMs and guardrail models to these subtle and sophisticated moral-aware attacks.
Activation-Guided Local Editing for Jailbreaking Attacks
Jiecong Wang | Haoran Li | Hao Peng | Ziqian Zeng | Zihao Wang | Haohua Du | Zhengtao Yu
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Jiecong Wang | Haoran Li | Hao Peng | Ziqian Zeng | Zihao Wang | Haohua Du | Zhengtao Yu
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
As Large Language Models (LLMs) become indispensable assistants, they remain vulnerable to misuse. Jailbreaking is an essential adversarial technique for red-teaming models to uncover and patch security flaws. However, existing jailbreak methods suffer from significant limitations. Token-level jailbreak attacks often produce incoherent or unreadable inputs and exhibit poor transferability, while prompt-level attacks lack scalability and rely heavily on manual effort and human ingenuity. We propose AGILE, a concise and effective two-stage framework that combines the advantages of these approaches. The first stage performs a one-shot, scenario-based generation of context and rephrases the original malicious query to obscure its harmful intent. The second stage utilizes information from the model’s hidden states to guide fine-grained edits, effectively steering the model’s internal representation of the input from a malicious one toward a benign one. Extensive experiments demonstrate that AGILE achieves state-of-the-art Attack Success Rate, with gains of up to 37.74% over the strongest baseline, and AGILE exhibits excellent transferability to black-box and large-scale models. Our code is available at https://github.com/SELGroup/AGILE.
SafeMT: Multi-turn Safety for Multimodal Language Models
Han Zhu | Juntao Dai | Jiaming Ji | Haoran Li | Chengkun Cai | Pengcheng Wen | Chi-Min Chan | Boyuan Chen | Yaodong Yang | Sirui Han | Yike Guo
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Han Zhu | Juntao Dai | Jiaming Ji | Haoran Li | Chengkun Cai | Pengcheng Wen | Chi-Min Chan | Boyuan Chen | Yaodong Yang | Sirui Han | Yike Guo
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
With the widespread use of multi-modal Large Language models (MLLMs), safety issues have become a growing concern. Multi-turn dialogues, which are more common in everyday interactions, pose a greater risk than single prompts; however, existing benchmarks do not adequately consider this situation. To encourage the community to focus on the safety issues of these models in multi-turn dialogues, we introduce SafeMT, a benchmark that features dialogues of varying lengths generated from harmful queries accompanied by images. This benchmark consists of 10,000 samples in total, encompassing 17 different scenarios and four jailbreak methods. Additionally, we propose Safety Index (SI) to evaluate the general safety of MLLMs during conversations. We assess the safety of 17 models using this benchmark and discover that the risk of successful attacks on these models increases as the number of turns in harmful dialogues rises. This observation indicates that the safety mechanisms of these models are inadequate for recognizing the hazard in dialogue interactions. We propose a dialogue safety moderator capable of detecting malicious intent concealed within conversations and providing MLLMs with relevant safety policies. Experimental results from several open-source models indicate that this moderator is more effective in reducing multi-turn Attack Success Rate (ASR) compared to existed guard models.
Robustness via Referencing: Defending against Prompt Injection Attacks by Referencing the Executed Instruction
Yulin Chen | Haoran Li | Yuan Sui | Yue Liu | Yufei He | Xiaoling Bai | Chi Fei | Li Yabo | Haozhe Ma | Yangqiu Song | Bryan Hooi
Findings of the Association for Computational Linguistics: ACL 2026
Yulin Chen | Haoran Li | Yuan Sui | Yue Liu | Yufei He | Xiaoling Bai | Chi Fei | Li Yabo | Haozhe Ma | Yangqiu Song | Bryan Hooi
Findings of the Association for Computational Linguistics: ACL 2026
Prompt injection attacks manipulate large language models (LLMs) by misleading them to deviate from the original input instructions and execute maliciously injected instructions, because of their instruction-following capabilities and inability to distinguish between the original input instructions and maliciously injected instructions. Currently, various prompt injection defense methods have been proposed, including prompt-engineering-based approaches and fine-tuning methods. Most of these methods instruct the model to follow the original input instructions, suppressing its inherent tendencies to follow the injected instructions. However, experimental results reveal that suppressing the model’s instruction-following tendencies is challenging. After analyzing successful attack cases, we find that the LLMs can correctly reference the instructions they are executing in some cases. Motivated by this finding, we propose a defense method that leverages LLMs’ instruction-following abilities rather than suppressing them. Our approach prompts LLMs to generate responses that include both the answers and their corresponding instruction references. Based on these references, we filter out answers whose references are not to the original input instructions. We conduct comprehensive experiments to evaluate the effectiveness of our proposed method. The results show that our approach outperforms prompt-engineering-based baselines and is comparable to fine-tuning methods, reducing the ASR to nearly 0% in some scenarios. Moreover, our approach has minimal impact on overall utility.
OmniCompliance-100K: A Multi-Domain, Rule-Grounded, Real-World Safety Compliance Dataset
Wenbin Hu | Huihao Jing | Haochen Shi | Changxuan Fan | Haoran Li | Yangqiu Song
Findings of the Association for Computational Linguistics: ACL 2026
Wenbin Hu | Huihao Jing | Haochen Shi | Changxuan Fan | Haoran Li | Yangqiu Song
Findings of the Association for Computational Linguistics: ACL 2026
Ensuring the safety and compliance of large language models (LLMs) is of paramount importance. However, existing LLM safety datasets often rely on ad-hoc taxonomies for data generation and suffer from a significant shortage of rule-grounded, real-world cases that are essential for robustly protecting LLMs. In this work, we address this critical gap by constructing a comprehensive safety dataset from a compliance perspective. Using a powerful web-searching agent, we collect a rule-grounded, real-world case dataset OmniCompliance-100K, sourced from multi-domain authoritative references. The dataset spans 74 regulations and policies across a wide range of domains, including security and privacy regulations, content safety and user data privacy policies from leading AI companies and social media platforms, financial security requirements, medical device risk management standards, educational integrity guidelines, and protections of fundamental human rights. In total, our dataset contains 12,985 distinct rules and 106,009 associated real-world compliance cases. Our analysis confirms a strong alignment between the rules and their corresponding cases. We further conduct extensive benchmarking experiments to evaluate the safety and compliance capabilities of advanced LLMs across different model scales. Our experiments reveal several interesting findings that have great potential to offer valuable insights for future LLM safety research.
GrandGuard: Taxonomy, Benchmark, and Safeguards for Elderly-Chatbot Interaction Safety
Changxuan Fan | Xi Yang | Yueyuan Zheng | Bin Zhou | Yuanping Wang | Wenbin Hu | Huihao Jing | Ki Sen Hung | Dazhao Du | Haoran Li | Janet Hui-wen Hsiao | Yangqiu Song
Findings of the Association for Computational Linguistics: ACL 2026
Changxuan Fan | Xi Yang | Yueyuan Zheng | Bin Zhou | Yuanping Wang | Wenbin Hu | Huihao Jing | Ki Sen Hung | Dazhao Du | Haoran Li | Janet Hui-wen Hsiao | Yangqiu Song
Findings of the Association for Computational Linguistics: ACL 2026
As older adults increasingly use LLM-based chatbots for companionship and assistance, a safety gap is emerging. Older adults may face vulnerabilities from social isolation, limited digital literacy, and cognitive decline, yet existing safety benchmarks largely target general harms and overlook elderly-specific risks. For example, a prompt such as “how to repair a ceiling light alone in the dark” may be benign for most users but poses a serious fall risk for older adults with mobility limitations.We introduce GrandGuard, the first comprehensive framework for assessing and mitigating elderly-specific contextual risks in LLM interactions. We develop a three-level taxonomy with 50 fine-grained risk types across mental well-being, financial, medical, toxicity, and privacy domains, grounded in real-world incidents, community discussions, and analysis of stakeholder studies. Using this taxonomy, we construct a benchmark of 10,404 labeled prompts and responses, showing that several leading LLMs mishandle elderly-specific contextual risks in over 50% of cases. We mitigate these failures with two safeguards: a fine-tuned Llama-Guard-3 and a policy-enhanced gpt-oss-safeguard-20b, achieving up to 96.2% and 90.9% unsafe-prompt detection accuracy, respectively. GrandGuard lays the groundwork for AI systems that move beyond general safety to support aging populations.
Mathematical Proof as a Litmus Test: Revealing Failure Modes of Advanced Large Reasoning Models
Dadi Guo | Jiayu Liu | Zhiyuan Fan | Zhitao He | Haoran Li | Yuxin Li | Yumeng Wang | Yi R. Fung
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Dadi Guo | Jiayu Liu | Zhiyuan Fan | Zhitao He | Haoran Li | Yuxin Li | Yumeng Wang | Yi R. Fung
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Large reasoning models ( e.g., R1, o3) have demonstrated remarkable mathematical problem-solving abilities. However, the high reported accuracy of these advanced models on popular datasets and reliance on purely numerical evaluation often mask their true reasoning shortcomings. To address this, we propose leveraging the inherent rigor and methodological complexity of mathematical proofs as a diagnostic tool to expose these hidden failures. Specifically, we introduce the RFMDataset (Reveal Failure Modes), a collection of 200 diverse mathematical proof problems to thoroughly evaluate the performance of advanced models. Our in-depth analysis of their failures uncovers 10 fine-grained error types, which shows fundamental limitations in current large reasoning models: 1) Large reasoning models still have limited capability in generating entirely correct mathematical proofs, with some models solving less than 20% of problems and even making mistakes on fundamental ones; 2) models exhibit a diverse spectrum of reasoning failures, prominently demonstrating the lack of guarantees for the correctness and rigor intermediate reasoning steps; and 3) models show hallucination and incompleteness during the reasoning process. Our findings also reveal that directly prompting models to self-reflect on specific failure modes is insufficient to resolve the current logical dilemmas, necessitating domain knowledge and formal verification.
ContextLens: Modeling Imperfect Privacy and Safety Context for Legal Compliance
Haoran Li | Yulin Chen | Huihao Jing | Wenbin Hu | Tsz Ho Li | Chanhou Lou | Hong Ting Tsang | Sirui Han | Yangqiu Song
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Haoran Li | Yulin Chen | Huihao Jing | Wenbin Hu | Tsz Ho Li | Chanhou Lou | Hong Ting Tsang | Sirui Han | Yangqiu Song
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Individuals’ concerns about data privacy and AI safety are highly contextualized and extend beyond sensitive patterns. Addressing these issues requires reasoning about the context to identify and mitigate potential risks. Though researchers have widely explored using large language models (LLMs) as evaluators for contextualized safety and privacy assessments, these efforts typically assume the availability of complete and clear context, whereas real-world contexts tend to be ambiguous and incomplete. In this paper, we propose ContextLens, a semi-rule-based framework that leverages LLMs to ground the input context in the legal domain and explicitly identify both known and unknown factors for legal compliance. Instead of directly assessing safety outcomes, our ContextLens instructs LLMs to answer a set of crafted questions that span over applicability, general principles and detailed provisions to assess compliance with pre-defined priorities and rules. We conduct extensive experiments on existing compliance benchmarks that cover the General Data Protection Regulation (GDPR) and the EU AI Act. The results suggest that our ContextLens can significantly improve LLMs’ compliance assessment and surpass existing baselines without any training. Additionally, our ContextLens can further identify the ambiguous and missing factors.
2025
On the Role of Entity and Event Level Conceptualization in Generalizable Reasoning: A Survey of Tasks, Methods, Applications, and Future Directions
Weiqi Wang | Tianqing Fang | Haochen Shi | Baixuan Xu | Wenxuan Ding | Liyu Zhang | Wei Fan | Jiaxin Bai | Haoran Li | Xin Liu | Yangqiu Song
Findings of the Association for Computational Linguistics: EMNLP 2025
Weiqi Wang | Tianqing Fang | Haochen Shi | Baixuan Xu | Wenxuan Ding | Liyu Zhang | Wei Fan | Jiaxin Bai | Haoran Li | Xin Liu | Yangqiu Song
Findings of the Association for Computational Linguistics: EMNLP 2025
Conceptualization, a fundamental element of human cognition, plays a pivotal role in human generalizable reasoning.Generally speaking, it refers to the process of sequentially abstracting specific instances into higher-level concepts and then forming abstract knowledge that can be applied in unfamiliar or novel situations. This enhances models’ inferential capabilities and supports the effective transfer of knowledge across various domains.Despite its significance, the broad nature of this term has led to inconsistencies in understanding conceptualization across various works, as there exists different types of instances that can be abstracted in a wide variety of ways.There is also a lack of a systematic overview that comprehensively examines existing works on the definition, execution, and application of conceptualization to enhance reasoning tasks.In this paper, we address these gaps by first proposing a categorization of different types of conceptualizations into four levels based on the types of instances being conceptualized, in order to clarify the term and define the scope of our work.Then, we present the first comprehensive survey of over 150 papers, surveying various definitions, resources, methods, and downstream applications related to conceptualization into a unified taxonomy, with a focus on the entity and event levels.Furthermore, we shed light on potential future directions in this field and hope to garner more attention from the community.
RewardDS: Privacy-Preserving Fine-Tuning for Large Language Models via Reward Driven Data Synthesis
Jianwei Wang | Chengming Shi | Junyao Yang | Haoran Li | Qianli Ma | Huiping Zhuang | Cen Chen | Ziqian Zeng
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Jianwei Wang | Chengming Shi | Junyao Yang | Haoran Li | Qianli Ma | Huiping Zhuang | Cen Chen | Ziqian Zeng
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
The success of large language models (LLMs) has attracted many individuals to fine-tune them for domain-specific tasks by uploading their data. However, in sensitive areas like healthcare and finance, privacy concerns often arise. One promising solution is to generate synthetic data with Differential Privacy (DP) guarantees to replace private data. However, these synthetic data contain significant flawed data, which are considered as noise. Existing solutions typically rely on naive filtering by comparing ROUGE-L scores or embedding similarities, which are ineffective in addressing the noise. To address this issue, we propose ***RewardDS***, a novel privacy-preserving framework that fine-tunes a reward proxy model and uses reward signals to guide the synthetic data generation. Our RewardDS introduces two key modules, Reward Guided Filtering and Self-Optimizing Refinement, to both filter and refine the synthetic data, effectively mitigating the noise. Extensive experiments across medical, financial, and code generation domains demonstrate the effectiveness of our method.
Context Reasoner: Incentivizing Reasoning Capability for Contextualized Privacy and Safety Compliance via Reinforcement Learning
Wenbin Hu | Haoran Li | Huihao Jing | Qi Hu | Ziqian Zeng | Sirui Han | Xu Heli | Tianshu Chu | Peizhao Hu | Yangqiu Song
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Wenbin Hu | Haoran Li | Huihao Jing | Qi Hu | Ziqian Zeng | Sirui Han | Xu Heli | Tianshu Chu | Peizhao Hu | Yangqiu Song
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
While Large Language Models (LLMs) exhibit remarkable capabilities, they also introduce significant safety and privacy risks. Current mitigation strategies often fail to preserve contextual reasoning capabilities in risky scenarios. Instead, they rely heavily on sensitive pattern matching to protect LLMs, which limits the scope. Furthermore, they overlook established safety and privacy standards, leading to systemic risks for legal compliance. To address these gaps, we formulate safety and privacy issues into contextualized compliance problems following the Contextual Integrity (CI) theory. Under the CI framework, we align our model with three critical regulatory standards: GDPR, EU AI Act, and HIPAA. Specifically, we employ reinforcement learning (RL) with a rule-based reward to incentivize contextual reasoning capabilities while enhancing compliance with safety and privacy norms. Through extensive experiments, we demonstrate that our method not only significantly enhances legal compliance (achieving a +8.58% accuracy improvement in safety/privacy benchmarks) but also further improves general reasoning capability. For OpenThinker-7B, a strong reasoning model that significantly outperforms its base model Qwen2.5-7B-Instruct across diverse subjects, our method enhances its general reasoning capabilities, with +2.05% and +8.98% accuracy improvement on the MMLU and LegalBench benchmark, respectively.
Can Indirect Prompt Injection Attacks Be Detected and Removed?
Yulin Chen | Haoran Li | Yuan Sui | Yufei He | Yue Liu | Yangqiu Song | Bryan Hooi
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Yulin Chen | Haoran Li | Yuan Sui | Yufei He | Yue Liu | Yangqiu Song | Bryan Hooi
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Prompt injection attacks manipulate large language models (LLMs) by misleading them to deviate from the original input instructions and execute maliciously injected instructions, because of their instruction-following capabilities and inability to distinguish between the original input instructions and maliciously injected instructions. To defend against such attacks, recent studies have developed various detection mechanisms. If we restrict ourselves specifically to works which perform detection rather than direct defense, most of them focus on direct prompt injection attacks, while there are few works for the indirect scenario, where injected instructions are indirectly from external tools, such as a search engine. Moreover, current works mainly investigate injection detection methods and pay less attention to the post-processing method that aims to mitigate the injection after detection.In this paper, we investigate the feasibility of detecting and removing indirect prompt injection attacks, and we construct a benchmark dataset for evaluation. For detection, we assess the performance of existing LLMs and open-source detection models, and we further train detection models using our crafted training datasets. For removal, we evaluate two intuitive methods: (1) the *segmentation removal method*, which segments the injected document and removes parts containing injected instructions, and (2) the *extraction removal method*, which trains an extraction model to identify and remove injected instructions.
PrivaCI-Bench: Evaluating Privacy with Contextual Integrity and Legal Compliance
Haoran Li | Wenbin Hu | Huihao Jing | Yulin Chen | Qi Hu | Sirui Han | Tianshu Chu | Peizhao Hu | Yangqiu Song
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Haoran Li | Wenbin Hu | Huihao Jing | Yulin Chen | Qi Hu | Sirui Han | Tianshu Chu | Peizhao Hu | Yangqiu Song
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Recent advancements in generative large language models (LLMs) have enabled wider applicability, accessibility, and flexibility. However, their reliability and trustworthiness are still in doubt, especially for concerns regarding individuals’ data privacy. Great efforts have been made on privacy by building various evaluation benchmarks to study LLMs’ privacy awareness and robustness from their generated outputs to their hidden representations. Unfortunately, most of these works adopt a narrow formulation of privacy and only investigate personally identifiable information (PII). In this paper, we follow the merit of the Contextual Integrity (CI) theory, which posits that privacy evaluation should not only cover the transmitted attributes but also encompass the whole relevant social context through private information flows. We present PrivaCI-Bench, a comprehensive contextual privacy evaluation benchmark targeted at legal compliance to cover well-annotated privacy and safety regulations, real court cases, privacy policies, and synthetic data built from the official toolkit to study LLMs’ privacy and safety compliance. We evaluate the latest LLMs, including the recent reasoner models QwQ-32B and Deepseek R1. Our experimental results suggest that though LLMs can effectively capture key CI parameters inside a given context, they still require further advancements for privacy compliance.
MCIP: Protecting MCP Safety via Model Contextual Integrity Protocol
Huihao Jing | Haoran Li | Wenbin Hu | Qi Hu | Xu Heli | Tianshu Chu | Peizhao Hu | Yangqiu Song
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Huihao Jing | Haoran Li | Wenbin Hu | Qi Hu | Xu Heli | Tianshu Chu | Peizhao Hu | Yangqiu Song
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
As Model Context Protocol (MCP) introduces an easy-to-use ecosystem for users and developers, it also brings underexplored safety risks. Its decentralized architecture, which separates clients and servers, poses unique challenges for systematic safety analysis. This paper proposes a novel framework to enhance MCP safety. Guided by the MAESTRO framework, we first analyze the missing safety mechanisms in MCP, and based on this analysis, we propose the Model Contextual Integrity Protocol (MCIP), a refined version of MCP that addresses these gaps. Next, we develop a fine-grained taxonomy that captures a diverse range of unsafe behaviors observed in MCP scenarios. Building on this taxonomy, we develop benchmark and training data that support the evaluation and improvement of LLMs’ capabilities in identifying safety risks within MCP interactions. Leveraging the proposed benchmark and training data, we conduct extensive experiments on state-of-the-art LLMs. The results highlight LLMs’ vulnerabilities in MCP interactions and demonstrate that our approach substantially improves their safety performance.
InteGround: On the Evaluation of Verification and Retrieval Planning in Integrative Grounding
Cheng Jiayang | Qianqian Zhuang | Haoran Li | Chunkit Chan | Xin Liu | Lin Qiu | Yangqiu Song
Findings of the Association for Computational Linguistics: EMNLP 2025
Cheng Jiayang | Qianqian Zhuang | Haoran Li | Chunkit Chan | Xin Liu | Lin Qiu | Yangqiu Song
Findings of the Association for Computational Linguistics: EMNLP 2025
Grounding large language models (LLMs) in external knowledge sources is a promising method for faithful prediction. While existing grounding approaches work well for simple queries, many real-world information needs require synthesizing multiple pieces of evidence. We introduce “integrative grounding” – the challenge of retrieving and verifying multiple inter-dependent pieces of evidence to support a hypothesis query. To systematically study this problem, we repurpose data from four domains for evaluating integrative grounding capabilities. Our investigation reveals two critical findings: First, in groundedness verification, while LLMs are robust to redundant evidence, they tend to rationalize using internal knowledge when information is incomplete. Second, in examining retrieval planning strategies, we find that undirected planning can degrade performance through noise introduction, while premise abduction emerges as a promising approach due to its logical constraints. Additionally, LLMs’ zero-shot self-reflection capabilities consistently improve grounding quality. These insights provide valuable direction for developing more effective integrative grounding systems.
PrivacyRestore: Privacy-Preserving Inference in Large Language Models via Privacy Removal and Restoration
Ziqian Zeng | Jianwei Wang | Junyao Yang | Zhengdong Lu | Haoran Li | Huiping Zhuang | Cen Chen
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Ziqian Zeng | Jianwei Wang | Junyao Yang | Zhengdong Lu | Haoran Li | Huiping Zhuang | Cen Chen
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
The widespread usage of online Large Language Models (LLMs) inference services has raised significant privacy concerns about the potential exposure of private information in user inputs. Existing privacy protection methods for LLMs suffer from either insufficient privacy protection with performance degradation, or large inference time overhead. To address these limitations, we propose PrivacyRestore, a plug-and-play method to protect the privacy of user inputs during LLM inference for the client-server scenario. The server first trains restoration vectors for each privacy span type offline and then releases them to the clients. During inference, the client aggregates restoration vectors of all privacy spans in the user query into a meta restoration vector, which is later sent to the server to restore information. Before transmission, the client removes all privacy spans in the user query and applies d𝜒-privacy mechanism to the meta vector for privacy protection. We prove that our method can inherently prevent the linear growth of the privacy budget. We conduct extensive experimental, covering the medical and legal domains, and demonstrate that PrivacyRestore effectively protects private information and maintains acceptable levels of performance and inference efficiency
Privacy Checklist: Privacy Violation Detection Grounding on Contextual Integrity Theory
Haoran Li | Wei Fan | Yulin Chen | Cheng Jiayang | Tianshu Chu | Xuebing Zhou | Peizhao Hu | Yangqiu Song
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)
Haoran Li | Wei Fan | Yulin Chen | Cheng Jiayang | Tianshu Chu | Xuebing Zhou | Peizhao Hu | Yangqiu Song
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)
Privacy research has attracted wide attention as individuals worry that their private data can be easily leaked during interactions with smart devices, social platforms, and AI applications. Existing works mostly consider privacy attacks and defenses on various sub-fields. Within each field, various privacy attacks and defenses are studied to address patterns of personally identifiable information (PII). In this paper, we argue that privacy is not solely about PII patterns. We ground on the Contextual Integrity (CI) theory which posits that people’s perceptions of privacy are highly correlated with the corresponding social context. Based on such an assumption, we formulate privacy as a reasoning problem rather than naive PII matching. We develop the first comprehensive checklist that covers social identities, private attributes, and existing privacy regulations. Unlike prior works on CI that either cover limited expert annotated norms or model incomplete social context, our proposed privacy checklist uses the whole Health Insurance Portability and Accountability Act of 1996 (HIPAA) as an example, to show that we can resort to large language models (LLMs) to completely cover the HIPAA’s regulations. Additionally, our checklist also gathers expert annotations across multiple ontologies to determine private information including but not limited to PII. We use our preliminary results on the HIPAA to shed light on future context-centric privacy research to cover more privacy regulations, social norms and standards. We will release the reproducible code and data.
Backdoor-Powered Prompt Injection Attacks Nullify Defense Methods
Yulin Chen | Haoran Li | Yuan Sui | Yangqiu Song | Bryan Hooi
Findings of the Association for Computational Linguistics: EMNLP 2025
Yulin Chen | Haoran Li | Yuan Sui | Yangqiu Song | Bryan Hooi
Findings of the Association for Computational Linguistics: EMNLP 2025
With the development of technology, large language models (LLMs) have dominated the downstream natural language processing (NLP) tasks. However, because of the LLMs’ instruction-following abilities and inability to distinguish the instructions in the data content, such as web pages from search engines, the LLMs are vulnerable to prompt injection attacks. These attacks trick the LLMs into deviating from the original input instruction and executing the attackers’ target instruction. Recently, various instruction hierarchy defense strategies are proposed to effectively defend against prompt injection attacks via fine-tuning.In this paper, we explore more vicious attacks that nullify the prompt injection defense methods, even the instruction hierarchy: backdoor-powered prompt injection attacks, where the attackers utilize the backdoor attack for prompt injection attack purposes. Specifically, the attackers poison the supervised fine-tuning samples and insert the backdoor into the model. Once the trigger is activated, the backdoored model executes the injected instruction surrounded by the trigger. We construct a benchmark for comprehensive evaluation. Our experiments demonstrate that backdoor-powered prompt injection attacks are more harmful than previous prompt injection attacks, nullifying existing prompt injection defense methods, even the instruction hierarchy techniques.
TopicAttack: An Indirect Prompt Injection Attack via Topic Transition
Yulin Chen | Haoran Li | Yuexin Li | Yue Liu | Yangqiu Song | Bryan Hooi
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Yulin Chen | Haoran Li | Yuexin Li | Yue Liu | Yangqiu Song | Bryan Hooi
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Large language models (LLMs) have shown remarkable performance across a range of NLP tasks. However, their strong instruction-following capabilities and inability to distinguish instructions from data content make them vulnerable to indirect prompt injection attacks. In such attacks, instructions with malicious purposes are injected into external data sources, such as web documents. When LLMs retrieve this injected data through tools, such as a search engine and execute the injected instructions, they provide misled responses. Recent attack methods have demonstrated potential, but their abrupt instruction injection often undermines their effectiveness. Motivated by the limitations of existing attack methods, we propose **TopicAttack**, which prompts the LLM to generate a fabricated conversational transition prompt that gradually shifts the topic toward the injected instruction, making the injection smoother and enhancing the plausibility and success of the attack. Through comprehensive experiments, TopicAttack achieves state-of-the-art performance, with an attack success rate (ASR) over 90% in most cases, even when various defense methods are applied. We further analyze its effectiveness by examining attention scores. We find that a higher injected-to-original attention ratio leads to a greater success probability, and our method achieves a much higher ratio than the baseline methods.
Defense Against Prompt Injection Attack by Leveraging Attack Techniques
Yulin Chen | Haoran Li | Zihao Zheng | Dekai Wu | Yangqiu Song | Bryan Hooi
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Yulin Chen | Haoran Li | Zihao Zheng | Dekai Wu | Yangqiu Song | Bryan Hooi
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
With the advancement of technology, large language models (LLMs) have achieved remarkable performance across various natural language processing (NLP) tasks, powering LLM-integrated applications like Microsoft Copilot. However, as LLMs continue to evolve, new vulnerabilities, especially prompt injection attacks arise. These attacks trick LLMs into deviating from the original input instructions and executing the attacker’s instructions injected in data content, such as retrieved results. Recent attack methods leverage LLMs’ instruction-following abilities and their inabilities to distinguish instructions injected in the data content, and achieve a high attack success rate (ASR). When comparing the attack and defense methods, we interestingly find that they share similar design goals, of inducing the model to ignore unwanted instructions and instead to execute wanted instructions. Therefore, we raise an intuitive question: *Could these attack techniques be utilized for defensive purposes?* In this paper, we invert the intention of prompt injection methods to develop novel defense methods based on previous training-free attack methods, by repeating the attack process but with the original input instruction rather than the injected instruction. Our comprehensive experiments demonstrate that our defense techniques outperform existing defense approaches, achieving state-of-the-art results.
2024
NegotiationToM: A Benchmark for Stress-testing Machine Theory of Mind on Negotiation Surrounding
Chunkit Chan | Cheng Jiayang | Yauwai Yim | Zheye Deng | Wei Fan | Haoran Li | Xin Liu | Hongming Zhang | Weiqi Wang | Yangqiu Song
Findings of the Association for Computational Linguistics: EMNLP 2024
Chunkit Chan | Cheng Jiayang | Yauwai Yim | Zheye Deng | Wei Fan | Haoran Li | Xin Liu | Hongming Zhang | Weiqi Wang | Yangqiu Song
Findings of the Association for Computational Linguistics: EMNLP 2024
Large Language Models (LLMs) have sparked substantial interest and debate concerning their potential emergence of Theory of Mind (ToM) ability. Theory of mind evaluations currently focuses on testing models using machine-generated data or game settings prone to shortcuts and spurious correlations, which lacks evaluation of machine ToM ability in real-world human interaction scenarios. This poses a pressing demand to develop new real-world scenario benchmarks. We introduce NegotiationToM, a new benchmark designed to stress-test machine ToM in real-world negotiation surrounding covered multi-dimensional mental states (i.e., desires, beliefs, and intentions). Our benchmark builds upon the Belief-Desire-Intention (BDI) agent modeling theory and conducts the necessary empirical experiments to evaluate large language models. Our findings demonstrate that NegotiationToM is challenging for state-of-the-art LLMs, as they consistently perform significantly worse than humans, even when employing the chain-of-thought (CoT) method.
GoldCoin: Grounding Large Language Models in Privacy Laws via Contextual Integrity Theory
Wei Fan | Haoran Li | Zheye Deng | Weiqi Wang | Yangqiu Song
Proceedings of the 2024 Conference on Empirical Methods in Natural Language Processing
Wei Fan | Haoran Li | Zheye Deng | Weiqi Wang | Yangqiu Song
Proceedings of the 2024 Conference on Empirical Methods in Natural Language Processing
Privacy issues arise prominently during the inappropriate transmission of information between entities. Existing research primarily studies privacy by exploring various privacy attacks, defenses, and evaluations within narrowly predefined patterns, while neglecting that privacy is not an isolated, context-free concept limited to traditionally sensitive data (e.g., social security numbers), but intertwined with intricate social contexts that complicate the identification and analysis of potential privacy violations. The advent of Large Language Models (LLMs) offers unprecedented opportunities for incorporating the nuanced scenarios outlined in privacy laws to tackle these complex privacy issues. However, the scarcity of open-source relevant case studies restricts the efficiency of LLMs in aligning with specific legal statutes. To address this challenge, we introduce a novel framework, GoldCoin, designed to efficiently ground LLMs in privacy laws for judicial assessing privacy violations. Our framework leverages the theory of contextual integrity as a bridge, creating numerous synthetic scenarios grounded in relevant privacy statutes (e.g., HIPAA), to assist LLMs in comprehending the complex contexts for identifying privacy risks in the real world. Extensive experimental results demonstrate that GoldCoin markedly enhances LLMs’ capabilities in recognizing privacy risks across real court cases, surpassing the baselines on different judicial tasks.
2023
Sentence Embedding Leaks More Information than You Expect: Generative Embedding Inversion Attack to Recover the Whole Sentence
Haoran Li | Mingshi Xu | Yangqiu Song
Findings of the Association for Computational Linguistics: ACL 2023
Haoran Li | Mingshi Xu | Yangqiu Song
Findings of the Association for Computational Linguistics: ACL 2023
Sentence-level representations are beneficial for various natural language processing tasks. It is commonly believed that vector representations can capture rich linguistic properties. Currently, large language models (LMs) achieve state-of-the-art performance on sentence embedding. However, some recent works suggest that vector representations from LMs can cause information leakage. In this work, we further investigate the information leakage issue and propose a generative embedding inversion attack (GEIA) that aims to reconstruct input sequences based only on their sentence embeddings. Given the black-box access to a language model, we treat sentence embeddings as initial tokens’ representations and train or fine-tune a powerful decoder model to decode the whole sequences directly. We conduct extensive experiments to demonstrate that our generative inversion attack outperforms previous embedding inversion attacks in classification metrics and generates coherent and contextually similar sentences as the original inputs.
2022
You Don’t Know My Favorite Color: Preventing Dialogue Representations from Revealing Speakers’ Private Personas
Haoran Li | Yangqiu Song | Lixin Fan
Proceedings of the 2022 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies
Haoran Li | Yangqiu Song | Lixin Fan
Proceedings of the 2022 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies
Social chatbots, also known as chit-chat chatbots, evolve rapidly with large pretrained language models. Despite the huge progress, privacy concerns have arisen recently: training data of large language models can be extracted via model inversion attacks. On the other hand, the datasets used for training chatbots contain many private conversations between two individuals. In this work, we further investigate the privacy leakage of the hidden states of chatbots trained by language modeling which has not been well studied yet. We show that speakers’ personas can be inferred through a simple neural network with high accuracy. To this end, we propose effective defense objectives to protect persona leakage from hidden states. We conduct extensive experiments to demonstrate that our proposed defense objectives can greatly reduce the attack accuracy from 37.6% to 0.5%. Meanwhile, the proposed objectives preserve language models’ powerful generation ability.
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- Yangqiu Song 19
- Yulin Chen 8
- Wenbin Hu 6
- Huihao Jing 6
- Bryan Hooi 5
- Tianshu Chu 4
- Wei Fan 4
- Sirui Han 4
- Peizhao Hu 4
- Ziqian Zeng 4
- Changxuan Fan 3
- Qi Hu 3
- Cheng Jiayang 3
- Xin Liu 3
- Yue Liu 3
- Yuan Sui 3
- Weiqi Wang 3
- Chunkit Chan 2
- Cen Chen 2
- Zheye Deng 2
- Yufei He 2
- Xu Heli 2
- Ki Sen Hung 2
- Haochen Shi 2
- Jianwei Wang 2
- Junyao Yang 2
- Xi Yang 2
- Huiping Zhuang 2
- Jiaxin Bai 1
- Xiaoling Bai 1
- Chengkun Cai 1
- Chi-Min Chan 1
- Kejiang Chen 1
- Boyuan Chen (陈博远) 1
- Juntao Dai 1
- Weili Diao 1
- Wenxuan Ding 1
- Haohua Du 1
- Dazhao Du 1
- Lixin Fan 1
- Zhiyuan Fan 1
- Tianqing Fang 1
- Chi Fei 1
- Yi R. Fung 1
- Yike Guo 1
- Dadi Guo 1
- Zhitao He 1
- Janet Hui-wen Hsiao 1
- Jiaming Ji 1
- Tsun On Kwok 1
- Xiaomeng Li 1
- Yuexin Li 1
- Yuxin Li 1
- Tsz Ho Li 1
- Chang Liu 1
- Jiayu Liu 1
- Chanhou Lou 1
- Zhengdong Lu 1
- Qianli Ma 1
- Haozhe Ma 1
- Zheng Mingen 1
- Hao Peng 1
- Lin Qiu 1
- Chengming Shi 1
- Ying Su 1
- Hong Ting Tsang 1
- Jiecong Wang 1
- Zihao Wang 1
- Yuanping Wang 1
- Yumeng Wang 1
- Pengcheng Wen 1
- Dekai Wu 1
- Baixuan Xu 1
- Mingshi Xu 1
- Li Yabo 1
- Yaodong Yang (杨耀东) 1
- Yauwai Yim 1
- Zhengtao Yu (余正涛) 1
- Liyu Zhang 1
- Weiming Zhang 1
- Hongming Zhang 1
- Zihao Zheng 1
- Yueyuan Zheng 1
- Xuebing Zhou 1
- Bin Zhou 1
- Han Zhu 1
- Qianqian Zhuang 1