Breaking ReAct Agents: Foot-in-the-Door Attack Will Get You In

Itay Nakash, George Kour, Guy Uziel, Ateret Anaby Tavor


Abstract
Following the advancement of large language models (LLMs), the development of LLM-based autonomous agents has become prevalent.As a result, the need to understand the security vulnerabilities of these agents has become a critical task. We examine how ReAct agents can be exploited using a straightforward yet effective method we refer to as the foot-in-the-door attack.Our experiments show that indirect prompt injection attacks, prompted by harmless and unrelated requests (such as basic calculations) can significantly increase the likelihood of the agent performing subsequent malicious actions.Our results show that once a ReAct agent’s thought includes a specific tool or action, the likelihood of executing this tool in the subsequent steps increases significantly, as the agent seldom re-evaluates its actions. Consequently, even random, harmless requests can establish a ‘foot-in-the-door’, allowing an attacker to embed malicious instructions into the agent’s thought process, making it more susceptible to harmful directives.To mitigate this vulnerability, we propose implementing a simple reflection mechanism that prompts the agent to reassess the safety of its actions during execution, which can help reduce the success of such attacks.
Anthology ID:
2025.findings-naacl.363
Volume:
Findings of the Association for Computational Linguistics: NAACL 2025
Month:
April
Year:
2025
Address:
Albuquerque, New Mexico
Editors:
Luis Chiruzzo, Alan Ritter, Lu Wang
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
6484–6509
Language:
URL:
https://preview.aclanthology.org/fix-sig-urls/2025.findings-naacl.363/
DOI:
Bibkey:
Cite (ACL):
Itay Nakash, George Kour, Guy Uziel, and Ateret Anaby Tavor. 2025. Breaking ReAct Agents: Foot-in-the-Door Attack Will Get You In. In Findings of the Association for Computational Linguistics: NAACL 2025, pages 6484–6509, Albuquerque, New Mexico. Association for Computational Linguistics.
Cite (Informal):
Breaking ReAct Agents: Foot-in-the-Door Attack Will Get You In (Nakash et al., Findings 2025)
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PDF:
https://preview.aclanthology.org/fix-sig-urls/2025.findings-naacl.363.pdf