ResearchResearch paperLarge Language Models · Efficiency & Inference1 source · Oct 8, 2026

Cancerous Backdoor Attack: Gradual Activation via Invisible Tokens and A Stage Controller

We present Cancerous Backdoor Attack, that gradually corrupts an LLM's reasoning over a sequence of interactions by leveraging invisible tokens and a stage controller.

Key points

  • Backdoor Attacks on Large Language Models (LLMs) typically follow a trigger-response pattern, where satisfying a trigger condition activates a single terminal behavior.
  • We evaluate Cancerous Backdoor Attack across several reasoning datasets.
  • We compare Cancerous Backdoor Attack with prior backdoor attack baselines to demonstrate our proposed attack outperforms the baselines.
  • Our results indicate that reasoning corruption can develop gradually before it becomes visible, making answer accuracy alone insufficient for detecting backdoor attacks.

Sources (1)

  • [1]Cancerous Backdoor Attack: Gradual Activation via Invisible Tokens and A Stage Controller
    arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 8, 07:05 PM
    We present Cancerous Backdoor Attack, that gradually corrupts an LLM's reasoning over a sequence of interactions by leveraging invisible tokens and a stage controller.
    Backdoor Attacks on Large Language Models (LLMs) typically follow a trigger-response pattern, where satisfying a trigger condition activates a single terminal behavior.

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