PR Security Review

Automated security analysis of pull request diffs. Focuses on security-specific concerns that generic code review misses: injection vulnerabilities, authentication bypasses, hardcoded secrets, and insecure data handling introduced by the change.

When to Use

• Before merging any PR that touches authentication, authorization, or session handling
• Before merging PRs that add or modify API endpoints
• When a PR processes user input, file uploads, or external data
• Before merging PRs that update security-sensitive dependencies
• As a final gate before releasing to production

When NOT to Use

Prerequisites

• Access to the PR diff (via get_diff or get_files GitHub MCP methods)
• Understanding of the application's trust boundary (what data is user-controlled)

Workflow

1. Fetch the PR diff

# Using GitHub MCP (built-in to Copilot CLI)
get_diff(owner, repo, pullNumber)

# Or review changed files
get_files(owner, repo, pullNumber)

2. Identify the attack surface in the diff

Before scanning for specific vulnerabilities, map what the PR adds or changes:

Attack surface checklist (mark relevant items):
[ ] New API endpoints or routes
[ ] Changes to authentication logic
[ ] Changes to authorization / permission checks
[ ] New or modified database queries
[ ] User input processing (form data, URL params, file uploads)
[ ] New dependencies added (check each with npm audit / pip-audit)
[ ] Environment variable / config changes
[ ] Cryptographic operations (hashing, encryption, token generation)
[ ] File system access
[ ] External HTTP requests

Only continue with checks relevant to the PR's actual attack surface.

3. Scan for injection vulnerabilities

# Fetch the PR diff first
$diff = gh pr diff <number>

# A03 — SQL Injection: string concatenation in queries
$diff | Select-String -Pattern "query.*\+|exec.*\+|`.*\${"

# A03 — Command Injection: unsanitized input in shell execution
$diff | Select-String -Pattern "exec\(|spawn\(|child_process|subprocess"

# A07 — XSS: unsanitized output in HTML context
$diff | Select-String -Pattern "innerHTML|dangerouslySetInnerHTML|document\.write"

4. Scan for authentication and authorization issues

# Check for missing auth middleware on new routes
# Look for patterns like:
# router.get('/sensitive', handler)  ← no auth middleware
# vs
# router.get('/sensitive', authenticate, handler)  ← protected

# Check for hardcoded credentials in the diff
$diff | Select-String -Pattern "password\s*=\s*['\`"]|secret\s*=\s*['\`"]|api.key\s*=\s*['\`"]" -CaseSensitive:$false

# Check for tokens/keys in new config files
$diff | Select-String -Pattern "AKIA[0-9A-Z]{16}|ghp_[a-zA-Z0-9]{36}|sk-[a-zA-Z0-9]{48}"

5. Check new dependencies

For any new package added in the PR:

# After checking out the PR branch
npm audit --json 2>&1 | Select-Object -First 100

# Check the specific package
npm info <package-name> dist-tags

Flag packages that:

• Have known CVEs in npm audit
• Have very few downloads or no maintenance
• Are unusual alternatives to well-known packages (potential typosquatting)

6. Review data flow for sensitive data

Trace user-controlled inputs through the diff:

Input sources (user-controlled):
→ req.body, req.params, req.query, req.headers
→ file uploads (req.files, multer)
→ WebSocket messages
→ URL paths

For each input: does it reach a dangerous sink without sanitization?
Dangerous sinks: database queries, shell execution, HTML output, file paths, eval()

7. Write the security review comment

Structure findings by severity:

## Security Review — PR #[number]

### 🔴 Critical (Block merge)
- **[SQL Injection]** `src/db/users.ts:42` — User-controlled `id` concatenated
  into raw SQL query. Use parameterized queries.
  ```typescript
  // Current (vulnerable)
  db.query(`SELECT * FROM users WHERE id = ${req.params.id}`)
  // Fix
  db.query('SELECT * FROM users WHERE id = ?', [req.params.id])
  ```

### 🟠 High (Fix this sprint)

- **[Missing Auth]** `src/api/admin.ts:15` — New `/admin/export` endpoint has
  no authentication middleware. Add `requireAdmin` middleware.

### 🟡 Medium (Fix next sprint)

- **[Weak Crypto]** `src/auth/token.ts:8` — Using `Math.random()` for token
  generation. Use `crypto.randomBytes(32)` instead.

### ✅ No issues found in

- Dependency changes (npm audit clean)
- Database queries (all parameterized)

Severity Classification

OWASP Top 10 Quick Reference

Common Rationalizations

Red Flags

• A new route is added without any mention of auth middleware in the diff
• eval(), exec(), or child_process.spawn() added with user input
• A new *.env file or secrets file added to the repository
• Dependencies added that are unusual variations of popular package names
• JWT or token validation logic changed or simplified
• New Access-Control-Allow-Origin: * header
• SSRF protections only block plain 127.0.0.1 or exact hostnames, but do not normalize encoded IP literals such as 2130706433 or 0x7f.0.0.1
• SSRF allowlists or denylists compare raw hostnames without handling trailing-dot forms such as internal.example.com.

Verification

• Attack surface mapped (all relevant categories identified)
• No injection vulnerabilities in new query/exec/eval calls
• All new API endpoints have appropriate auth middleware
• No secrets or API keys in the diff
• New dependencies pass npm audit --audit-level=high
• Sensitive data (passwords, tokens, PII) not logged
• Security findings communicated to PR author with specific line references

Tips

• Focus on the diff: you're reviewing what changed, not the whole codebase. A secure old function does not become a concern — a new insecure call does.
• Trace data flows: don't just grep for patterns. Follow user input from where it enters to where it lands.
• Use explore agent for deep analysis: "Find all places in this PR diff where req.body is used without validation."
• Escalate confirmed Critical/High findings to the security team — don't merge.

See Also

• security-scan — full codebase scan (not just PR diff)
• evaluate-repository — 7-dimension repo security scorecard
• secret-detection — dedicated secret scanning
• input-validation — sanitization patterns for fixing findings