What is Cross-Site Scripting (XSS) and how can you prevent it in a web application?

What is Cross-Site Scripting (XSS) and how can you prevent it in a web application?

Cross-Site Scripting (XSS) is a type of security vulnerability in web applications where malicious scripts are injected into otherwise trusted websites. This can lead to attacks such as stealing sensitive information or session hijacking.

To prevent XSS in a web application, developers can implement various measures:

1. Input Validation: Validate and sanitize all user inputs, such as form submissions, to ensure that they do not contain harmful scripts.
2. Output Encoding: Encode user-generated content before displaying it on the website to prevent it from being interpreted as executable code.
3. Content Security Policy (CSP): Implement a strict CSP to define the sources from which scripts can be executed, mitigating the risks of XSS attacks.
4. HTTP Only Cookies: Use HTTP Only attribute in cookies to prevent client-side scripts from accessing them, reducing the impact of XSS attacks.

By following these best practices and staying vigilant for potential vulnerabilities, developers can effectively prevent Cross-Site Scripting (XSS) attacks in web applications.