Code Review — Find Every Problem

Perform a thorough code review of the following code. Act as a senior engineer who is unforgiving about quality.

Review for:
1. Bugs and logic errors (including subtle ones)
2. Security vulnerabilities (injection, auth issues, data exposure, etc.)
3. Performance problems (N+1 queries, unnecessary loops, memory leaks)
4. Error handling gaps
5. Readability and maintainability issues
6. Violation of SOLID principles or relevant design patterns
7. Missing edge case handling

For each issue found:
- Severity: Critical / High / Medium / Low
- Line reference
- What the problem is
- Why it matters
- The corrected code

End with an overall assessment and the top 3 things to fix first.

CODE:
[paste code here]

Language: [language]
Context: [brief description of what this code does]