Steps to Secure a Web Application from Common Vulnerabilities

1. Validate and Sanitize User Inputs: Implement input validation to ensure that users provide only expected data. Use parameterized queries to prevent SQL injection attacks.

2. Use Prepared Statements: Utilize prepared statements to execute SQL queries safely and securely, reducing the risk of SQL injection attacks.

3. Implement Content Security Policy (CSP): Define a strict CSP to specify which resources can be loaded, thereby mitigating the risk of cross-site scripting attacks.

4. Secure Authentication and Authorization: Implement strong authentication mechanisms, such as multi-factor authentication, and ensure that users have appropriate access controls to prevent unauthorized access.

5. Regular Security Testing: Conduct regular security assessments, including penetration testing and code reviews, to identify and address potential vulnerabilities in the web application.

6. Stay Updated with Security Patches: Keep the web application and its dependencies up to date with the latest security patches to address known vulnerabilities and protect against potential threats.

By following these steps, you can significantly enhance the security of your web application and protect it from common vulnerabilities like SQL injection and cross-site scripting.