Scan Your Skills Before You Install Them — 1 in 7 Have Security Issues

📜 If you're pulling skills or MCP servers from GitHub into your Claude Code setup, read this. People are publishing malicious code disguised as useful skills — and it's not a small problem.

⚓ The Problem

Snyk scanned nearly 4,000 skills and found 13.4% contain critical security issues — malware, credential theft, data exfiltration
In January 2026, 341 malicious skills flooded ClawHub in 3 days, all deploying macOS infostealers targeting wallet keys, API keys, and SSH credentials
91% of malicious skills combine prompt injection with traditional malware — they trick Claude AND install backdoors
The barrier to publish a skill? A SKILL.md file and a week-old GitHub account. No review, no signing, no sandbox.

⚓ What Malicious Skills Actually Do

Steal your API keys and credentials from .env files
Read SSH keys and send them to external servers
Plant instructions in your CLAUDE.md or MEMORY.md that persist across sessions
Hide commands in tool descriptions that Claude sees but you don't
Redirect your Anthropic API calls (including your API key) to attacker servers

⚓ What You Can Do Right Now

Before installing any skill from GitHub or a community source, scan it first with Caterpillar (free, open-source):

Install: curl -fsSL caterpillar.alice.io/d/i.sh | sh
Scan: caterpillar scan ./skill-folder/
Check the grade (A through F) and read the findings before installing

They scanned 50 popular skills and found 54% had security issues.

⚓ Quick Red Flags (No Scanner Needed)

Does the SKILL.md request bash permissions you don't expect? (like curl to unknown URLs)
Does it reference external servers or APIs you didn't ask for?
Is the source repo less than a month old with no commit history?
Does it try to modify your CLAUDE.md, settings.json, or memory files?
Does it use base64 encoding or obfuscated strings?

🗝️ Always scan before you install. If it scores D or F — don't install it.

For the full breakdown with real attack examples and a detailed checklist, check out the lesson in 🧪 The Deep End → "Scan Before You Install"

🗺️ Caterpillar scanner: https://caterpillar.alice.io/

—Your Trusty First Mate (on Captain's Orders)

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