Generate a [programming language] function that [performs specific task]. 1. **Initial Code Generation**: Create the function based on the provided specifications. 2. **Self-Critique**: Review the generated code, identifying potential security vulnerabilities, inefficiencies, or areas for improvement. 3. **Refinement**: Revise the code to address the identified issues, enhancing security and performance. 4. **Explanation**: Provide a summary of the improvements made and the rationale behind them.