Skill Validator

Skill Validator

Purpose: Automatically audit skills (especially third-party/downloaded ones) to detect security risks, malicious patterns, and ensure compliance with the "Rich Skill" structure.

1. Red Flags (Anti-Rationalization)

STOP and READ THIS if you are thinking:

• "I can just read the files manually" -> WRONG. Malicious code can be obfuscated or hidden in long lines. EXECUTE the validator.
• "It's just a simple skill, no need to scan" -> WRONG. Simple skills are the easiest vector for supply chain attacks.
• "The validator found 0 issues, it must be safe" -> WRONG. The validator is a static analysis tool. It cannot catch everything. Use your judgment.
• "I'll skip the bash scanner because there are no .sh files" -> WRONG. Bash code can be embedded in SKILL.md examples or Python strings.
• "Prompts are just text, they can't be dangerous" -> WRONG. Prompt injection can override system instructions or generate harmful content.

2. Capabilities

• Structure Audit: Verifies SKILL.md frontmatter, required directories, and file integrity.
• Bash Scanning: Detects dangerous patterns (piping downloads to shell, recursive deletion, fork bombs).
• Static Analysis: Flags high-risk keywords (eval, exec, subprocess, os.system) across all files.
• Obfuscation Detection: Flags high-entropy strings and long lines that might hide malware.
• Base64 Payload Inspection: Decodes Base64 strings and re-scans decoded content for hidden threats.
• AI Safety Analysis: Detects prompt injection, jailbreak attempts ("DAN", "simulate unfiltered"), and harmful content instructions (opt-in via --ai-scan).
• PII & Credential Detection: Flags potential API keys (OpenAI, GitHub, AWS), emails, and IP addresses.
• Risk Level: Reports a risk assessment (SAFE/CAUTION/DANGER) based on scan findings.

3. Instructions

Phase 1: Scan

1. Run Full Audit (Recommended for Untrusted Skills):

This script runs all checks (including AI Scan), ignores .scanignore, and prompts you for Phase 3 verification if needed. ``bash python3 scripts/full_audit.py ``

1. Run Standard Scan (For Your Own Trusted Skills):

This respects .scanignore and runs faster (no AI scan by default). ``bash python3 scripts/validate.py ``

1. Analyze Report: Review the output.

• CRITICAL: Immediate blockers. DO NOT USE the skill.
• WARNING: Require manual verification.
• INFO: Suggestions for improvement.

1. Check Risk Level: If DANGER or CAUTION, perform Phase 2.

Phase 2: Manual Review (Adversarial)

1. Check Bash Scripts: If scripts/ contains bash files, read them carefully.

• Look for network calls that pipe to execution.
• Check for environment variable exfiltration.

1. Verify Obfuscation: If the validator flagged "High Entropy", check those lines. Are they legitimate assets (images/keys) or hidden code?

Phase 3: Agent-Assisted Verification (Advanced)

For deep analysis of prompts or suspicious text, use the extracted LLM prompts in references/prompts/.

1. Select Prompt: Choose jailbreak_check.md or alignment_check.md.
2. Instruct Agent: "Reference references/prompts/jailbreak_check.md and analyze the following text: [Text from Skill]"
3. Evaluate: The Agent will use the specialized prompt to detect subtle manipulation attempts that regex missed.

CLI Options

| Flag | Description | | :--- | :--- | | --json | Output results in structured JSON format (for CI/CD). | | --no-scanignore | Ignore .scanignore files. Use for untrusted skills. | | --strict | Exit code 2 on warnings (for CI/CD gating). | | --ai-scan | Enable AI threat detection (prompt injection, jailbreaks). | | --version | Print validator version. |

4. Workflows

graph TD
    %% Phase Definitions
    subgraph Phase1 [Phase 1: Automated Scan]
        A[Start: Skill Path] --> B{Structure Check}
        B -- Pass --> C[File Scan]
        C --> D[Bash Scanner]
        C --> E[Static Analyzer]
        E --> F[Payload Decoder]
        F --> G[Re-Scan Content]
        C -.->|--ai-scan| H[AI Threat Scanner]
        D & E & G & H --> I{Risk Calculation}
        I --> J[Generate Report]
    end

    subgraph Phase2 [Phase 2: Manual Review]
        L[Check Scripts & Obfuscation]
        L --> M{Is Malicious?}
    end

    subgraph Phase3 [Phase 3: Agent Verification]
        N[Suspicious/Ambiguous Content]
        N --> O[Agent-Assisted Prompt Analysis]
        O --> P[Agent Opinion]
    end

    subgraph Phase4 [Phase 4: Final Verdict]
        EndSafe[End: Safe]
        EndBlock[End: Block/Fix]
    end

    %% Connections
    J --> K{High Risk / Warnings?}
    K -- No --> EndSafe
    K -- Yes --> L
    
    M -- Yes --> EndBlock
    M -- No --> EndSafe
    M -- Unsure --> N

    P --> Q{Final Verdict}
    Q -- Safe --> EndSafe
    Q -- Unsafe --> EndBlock

    %% Styling
    style EndSafe fill:#d4edda,stroke:#155724,stroke-width:2px
    style EndBlock fill:#f8d7da,stroke:#721c24,stroke-width:2px

5. Security & Limitations

> [!WARNING] > Regex-based bypass: This scanner uses pattern matching. Attackers can bypass it with string splitting, variable indirection, encoding layers, or dynamic imports. See references/guidelines.md for known bypass techniques.

> [!CAUTION] > .scanignore risk: By default, .scanignore in the scanned skill is honored. For untrusted skills, ALWAYS use --no-scanignore to prevent attackers from hiding their malicious files.

• Static Only: This tool does not execute the skill. It reads the files.
• False Positives: It may flag legitimate security tools because they contain "attack patterns" for detection.
• File Size Limit: Files larger than 10MB are skipped to prevent OOM.
• Risk Level != Safety: A SAFE risk level means the scanner found no threats, NOT that the skill is guaranteed safe.

6. Resources

• scripts/validate.py: Main entry point.
• scripts/scanners/: Pluggable scanner modules.
• patterns.py: Shared pattern definitions.
• bash_scanner.py: Bash-specific scanner.
• static_analyzer.py: Static analysis, obfuscation, Base64 inspection.
• ai_scanner.py: AI threat detection (prompt injection, jailbreaks).
• structure_check.py: Structural validation.
• references/guidelines.md: OWASP patterns, CWE references, known bypass techniques.
• examples/usage_example.md: Complete usage walkthrough with sample outputs.
• assets/report_format_example.md: Suggested report format for downstream consumers.
• references/prompts/: LLM prompts for agent-assisted verification.
• jailbreak_check.md: Detects adversarial attacks.
• alignment_check.md: Verifies topical scope.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: MatrixFounder
• Source: MatrixFounder/Universal-skills
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.