vetskill scans Claude Code skills for hidden instructions and credential theft

A developer released vetskill, an open-source MIT tool (Python 3.10+, standard library only) that checks agent skills for Claude Code, Codex and Cursor before installation. It runs 21 deterministic offline rules to flag invisible Unicode instructions, reads of ~/.ssh and ~/.aws/credentials, data exfiltration and persistence in ~/.bashrc.

• 21 offline rules with no model; any high finding is a BLOCK with exit code 1 for CI
• Detects hidden Unicode tag characters, AWS/GitHub key reads and webhook uploads
• Review mode sends findings and the first 60 lines of SKILL.md to a model
• Ships 30 offline tests and a pdf-tidy example skill rated 100/100 risk