Backdoor Decontamination Dynamics in LLM Agents
Open-weight LLM agents are vulnerable to backdoors installed during fine-tuning, which may be undetectable if the trigger conditions are never met during testing. Assuming defenders do not know the existing trigger, they cannot unlearn it directly. One decontamination strategy is to install a known backdoor (defensive poisoning) then to unlearn it, hoping that the original unknown backdoor is removed as a side effect. However, this procedure has uncertain outcomes: the original backdoor may persist or be erased or rerouted, among other possibilities. We introduce a framework for studying these dynamics in tool-calling agents, decoupling trigger, response, teacher, and fine-tuning method a...
| Authors | Gabriel Huang, Abhay Puri, Léo Boisvert et al. |
|---|---|
| Primary category | cs.CR |
| Published | 11 August 2026 |
| Last updated at source | 11 August 2026 |
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