find-bugs
Find bugs, security vulnerabilities, and code quality issues in local branch changes. Use when asked to review changes, find bugs, security review, or audit code on the current branch.
When & Why to Use This Skill
This Claude skill automates the code review process by analyzing local branch changes for bugs, security vulnerabilities, and quality issues. It follows a rigorous multi-phase workflow—including attack surface mapping and a comprehensive security checklist (covering OWASP standards like Injection, XSS, and Auth)—to provide high-severity findings and actionable fix suggestions directly within the developer's workflow.
Use Cases
- Pre-merge security audit: Automatically scan feature branches for vulnerabilities like SQL injection, XSS, or improper authorization before opening a Pull Request.
- Bug hunting in complex diffs: Identifying logic errors, race conditions, or business logic flaws in large code changes that might be missed during manual inspection.
- Code quality enforcement: Ensuring new code adheres to security best practices and doesn't introduce technical debt, information disclosures, or insecure cryptographic patterns.
| name | find-bugs |
|---|---|
| description | Find bugs, security vulnerabilities, and code quality issues in local branch changes. Use when asked to review changes, find bugs, security review, or audit code on the current branch. |
Find Bugs
Review changes on this branch for bugs, security vulnerabilities, and code quality issues.
Phase 1: Complete Input Gathering
- Get the FULL diff:
git diff master...HEAD - If output is truncated, read each changed file individually until you have seen every changed line
- List all files modified in this branch before proceeding
Phase 2: Attack Surface Mapping
For each changed file, identify and list:
- All user inputs (request params, headers, body, URL components)
- All database queries
- All authentication/authorization checks
- All session/state operations
- All external calls
- All cryptographic operations
Phase 3: Security Checklist (check EVERY item for EVERY file)
- Injection: SQL, command, template, header injection
- XSS: All outputs in templates properly escaped?
- Authentication: Auth checks on all protected operations?
- Authorization/IDOR: Access control verified, not just auth?
- CSRF: State-changing operations protected?
- Race conditions: TOCTOU in any read-then-write patterns?
- Session: Fixation, expiration, secure flags?
- Cryptography: Secure random, proper algorithms, no secrets in logs?
- Information disclosure: Error messages, logs, timing attacks?
- DoS: Unbounded operations, missing rate limits, resource exhaustion?
- Business logic: Edge cases, state machine violations, numeric overflow?
Phase 4: Verification
For each potential issue:
- Check if it's already handled elsewhere in the changed code
- Search for existing tests covering the scenario
- Read surrounding context to verify the issue is real
Phase 5: Pre-Conclusion Audit
Before finalizing, you MUST:
- List every file you reviewed and confirm you read it completely
- List every checklist item and note whether you found issues or confirmed it's clean
- List any areas you could NOT fully verify and why
- Only then provide your final findings
Output Format
Prioritize: security vulnerabilities > bugs > code quality
Skip: stylistic/formatting issues
For each issue:
- File:Line - Brief description
- Severity: Critical/High/Medium/Low
- Problem: What's wrong
- Evidence: Why this is real (not already fixed, no existing test, etc.)
- Fix: Concrete suggestion
- References: OWASP, RFCs, or other standards if applicable
If you find nothing significant, say so - don't invent issues.
Do not make changes - just report findings. I'll decide what to address.