dev.to· Oct 29, 2026· by gabrielanhaia

Invisible Unicode in a Rules File Made Copilot and Cursor Write a Backdoor. Find It

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Zero-width, bidi and Unicode tag characters hid instructions in AI rules files. How they work, plus a ripgrep check and a git hook that block them.
🎯 Vulnerability: Web Security Vulnerability
💡 Defense Fix: Implement strict input validation, contextual output encoding, and enforce least-privilege authorization controls.
#security#ai#git#tutorial