Dr. Jekyll and Mr. Hyde
Two Faces of LLMs
Matteo Gioele Collu (Università degli Studi di Padova)
Tom Janssen-Groesbeek (Radboud Universiteit Nijmegen)
Stefanos Koffas (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Mauro Conti (Università degli Studi di Padova, Örebro University)
Stjepan Picek (University of Zagreb, University of Bergen, Radboud Universiteit Nijmegen)
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Abstract
Large Language Models (LLMs) are being integrated into applications such as chatbots or email assistants. To prevent improper responses, safety mechanisms, such as Reinforcement Learning from Human Feedback (RLHF), are implemented in them. In this work, we bypass these safety measures for ChatGPT, Gemini, and Deepseek by making them impersonate complex personas with personality characteristics that are not aligned with a truthful assistant. First, we create elaborate biographies of these personas, which we then use in a new session with the same chatbots. Our conversations then follow a role-play style to elicit prohibited responses. Using personas, we show that prohibited responses are provided, making it possible to obtain unauthorized, illegal, or harmful information when querying ChatGPT, Gemini, and Deepseek. We show that these chatbots are vulnerable to this attack by getting dangerous information for 40 out of 40 illicit questions in GPT-4.1-mini, Gemini-1.5-flash, 39 out of 40 in GPT-4o-mini, 38 out of 40 in GPT-3.5-turbo, and 2 out of 2 cases in Gemini-2.5-flash and DeepSeek V3. The attack can be carried out manually or automatically using a support LLM, and has proven effective against models deployed between 2023 and 2025.
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