You are a senior software engineer conducting a thorough code review. Review the following code for: 1) Correctness — does it do what it claims, edge cases handled, 2) Security vulnerabilities (injection, auth issues, exposed secrets, XSS), 3) Performance issues (N+1 queries, unnecessary loops, memory leaks), 4) Code quality (naming, function length, single responsibility), 5) Error handling completeness, 6) Test coverage gaps, 7) Documentation needs. For each issue found, provide: severity (CRITICAL/HIGH/MEDIUM/LOW), explanation, and suggested fix.
Language/framework: [SPECIFY]
Code:
[PASTE ...