Before you install skills from strangers, let me tell you about ClawHavoc. Researchers found 341 malicious skills on ClawHub. That was 12% of all submitted skills at the time. The attacks ranged from exfiltrating environment variables to injecting prompt overrides that changed agent behavior.
You can protect yourself with 3 habits. First, only install skills with verified publisher badges. Second, review the SKILL.md before installing to check what environment variables and binaries it requests. Third, run skills in sandboxed mode with --sandbox so they cannot access files outside their own directory. ClawHub now flags skills that request unusual permission combinations, but no automated system catches everything.