Rejection-to-Acceptance Transition: Model Editing-Based Jailbreak Backdoor Injection Not Limited to Few Output Tokens
Paper · 2026 · Shiji Yang, Min Cai, Hao Xiong et al.
Summary
The paper examines jailbreak backdoors planted in safety-aligned LLMs through lightweight model editing. Earlier editing attacks, such as JailbreakEdit, tie a trigger to compliant opening phrases like "Sure,". The model can still refuse later in its answer, and adding more bound phrases raises both run time and cost. The authors propose JEST, which instead edits the model's internal representations. They build a small contrastive set of harmful and benign prompt pairs. The harmful prompts are filtered with Llama-Guard-3-1B, and GLM-4-flash writes a benign counterpart for each. They then run PCA on differences in last-token, final-layer hidden states, which separates a "rejection domain" from an "acceptance domain." A locate-then-edit, closed-form update to one FFN layer makes the trigger move harmful-prompt representations into the acceptance region. A simple guided prompt engineering step (GPE) strengthens the attack further. Across several LLMs and datasets, JEST beats JailbreakEdit, and JEST+GPE usually reaches over 90% jailbreak success rate (JSR). The authors present this as evidence of how fragile LLM safety boundaries are and argue that stronger defenses are needed.
Key points
- Victim models: Llama-2-7b-chat-hf, Vicuna-v1.5-7b, ChatGLM2-6b, Llama-3-8b-Instruct and Mistral-7b-Instruct. Evaluation data includes Advbench and DAN.
- Ablation on Llama-2-7b-chat-hf (JSR):
- GPE alone adds roughly 20 points over the no-attack setting.
- JEST alone reaches up to 86.54%.
- JEST+GPE reaches up to 93.08%.
- Data needs: only a small amount of modeling data is required, and performance peaked at 70 samples. Five random draws of 70 samples gave JSR between 87.69% and 92.56% on DAN.
- Projection space: using only the top few principal components gives the best results. Adding more components tends to hurt, especially on Llama-2 and Mistral.
- Layer choice: editing early-to-mid layers yields the highest JSR, though overall sensitivity to the chosen layer is low.
Institutions
Fields, topics and concepts
📚 Shelves 4The field of science this work belongs to (OpenAlex fields).Computer Science · 18,614 worksArtificial Intelligence · 17,965 worksArts and Humanities · 17,450 worksLanguage and Linguistics · 17,296 works
🧭 Topics 1Research subjects and languages the work is about.Bias, fairness & safety · 587 works
Cite
Cite as Shiji Yang, Min Cai, Hao Xiong, Congyao Mei, Haodong Zou, Shicheng Tan, Jie Chen, Fulan Qian and Shu Zhao. 2026. Rejection-to-Acceptance Transition: Model Editing-Based Jailbreak Backdoor Injection Not Limited to Few Output Tokens. Findings of the Association for Computational Linguistics: ACL 2026.
@inproceedings{yang2026rejection,
title = {{Rejection-to-Acceptance Transition: Model Editing-Based Jailbreak Backdoor Injection Not Limited to Few Output Tokens}},
author = {Shiji Yang, Min Cai, Hao Xiong, Congyao Mei, Haodong Zou, Shicheng Tan, Jie Chen, Fulan Qian and Shu Zhao},
booktitle = {Findings of the Association for Computational Linguistics: ACL 2026},
year = {2026},
doi = {10.18653/v1/2026.findings-acl.1625},
url = {https://doi.org/10.18653/v1/2026.findings-acl.1625}
}References
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