Comprehensive Code Review

Please review the following code with attention to these areas:

1. **Code Quality**
   - Naming conventions and readability
   - Single responsibility principle
   - DRY (Don't Repeat Yourself) violations
   - Code comments and documentation

2. **Performance**
   - Unnecessary re-renders (React)
   - Memory leaks potential
   - N+1 query problems
   - Inefficient algorithms

3. **Security**
   - Input validation
   - SQL injection vulnerabilities
   - XSS vulnerabilities
   - Authentication/authorization issues
   - Sensitive data exposure

Please provide:
- Specific issues found with line references
- Severity level (Critical/High/Medium/Low)
- Suggested fixes with code examples
- Positive aspects of the code