The rapid proliferation of large language models and multimodal generative models has raised concerns about their potential vulnerabilities to a wide range of real-world safety risks. However, a critical gap persists in systematic assessment, alongside the lack of evaluation frameworks to keep pace with the breadth and variability of real-world risk factors. In this paper, we introduce TroGEN, an automated jailbreak prompt generation framework that assesses these vulnerabilities by deriving scenario-driven jailbreak prompts using an adversarial agent. Moving beyond labor-intensive dataset construction, TroGEN features an extensible design that covers broad range of risks, supports plug-and-play jailbreak strategies, and adapts seamlessly to multimodal settings. Experimental results demonstrate that TroGEN effectively uncovers safety weaknesses, revealing susceptibilities to adversarial attacks that conceal malicious intent beneath an apparently benign facade, like a Trojan horse. Furthermore, such stealthy attacks exhibit resilience even against existing jailbreak defense methods.