PuzzleMask Bypasses LLM Policy Guards Using Plain Prose

Forensic Summary

Check Point Research has disclosed PuzzleMask, a prompt-crafting technique that embeds policy-violating payloads inside ordinary English prose to fool lightweight LLM-based gatekeepers into classifying malicious input as benign. Tested against four commercial and open-source safety models, the technique achieved a 100% bypass rate on gatekeeper checks, with the downstream target model successfully extracting and acting on the hidden payload in over 90% of trials. The attack requires no special encoding, invisible characters, or emoji obfuscation, making it harder to detect with traditional content filters.

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Read the full technical deep-dive on Grid the Grey: https://gridthegrey.com/posts/puzzlemask-bypasses-llm-policy-guards-using-plain-prose/