Malicious Lean proof passed 10/11 tests — caught only by a regex check

ricklamers · x · 2026-09-24

@langstonnashold reveals a maliciously crafted Lean proof that passed 10 of 11 test cases and was caught only by a regex check (\bopen\b[^\n]\bLean\b). A full write-up is promised soon. @ricklamers notes that when regex is the last line of defense, your eval pipeline is in trouble.

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