poc: shell injection verification via skill directory name

[dorjoos]

Security verification PR — testing expression injection in skill-check.yml workflow.

This PR adds skills/$(printf RCE_CONFIRMED)/SKILL.md to verify that the ${{ steps.detect.outputs.skill_args }} expression in the 'Run skill-validator check' step evaluates shell command substitution when an attacker-controlled filename is used.

Expected: Running: .skill-validator/skill-validator check --verbose --skills skills/RCE_CONFIRMED appears in workflow logs, proving $(printf RCE_CONFIRMED) was executed.

[github-actions]

🔍 Skill Validator Results

2 resource(s) checked | ✅ All checks passed

Full output

Specify one of --plugin, --skills, or --agents. Use --plugin to check an entire plugin directory.

Note: Errors were found. These are currently reported as warnings and do not block merge. Please review and address when possible.

[dorjoos]

Closing test PR — research complete.