Unicode hidden character detection in .cursorrules and CLAUDE.md

[kobzevvv]

Rules File Backdoor (Pillar Security, March 2025): .cursorrules and CLAUDE.md files can contain zero-width joiners and bidirectional markers invisible to humans but parsed by the LLM. Agent generates backdoored code silently, persists across forks. Proposal: scan CLAUDE.md, .cursorrules, .github/copilot-instructions.md for Unicode control chars (U+200D, U+202E, U+2066-U+2069). Flag as HIGH severity. Reference: pillar.security/blog/new-vulnerability-in-github-copilot-and-cursor