XSS Prevention - OWASP Top 10

Cross-Site Scripting (XSS) is a security vulnerability that allows attackers to inject malicious scripts into content from otherwise trusted websites. XSS attacks can lead to the exposure of sensitive information and user data.

XSS is a type of injection attack where an attacker injects malicious scripts into content that is then served to users. This occurs when web applications accept user input without proper validation or escaping.

3.1 Stored XSS

In Stored XSS, the malicious script is stored on the server (e.g., in a database) and served to users when they request the affected content.

3.2 Reflected XSS

Reflected XSS occurs when the malicious script is reflected off a web server, typically via a URL or a form submission, and executed immediately in the user's browser.

3.3 DOM-based XSS

In DOM-based XSS, the vulnerability exists in the client-side code rather than the server-side. The malicious script is executed as a result of modifying the DOM.

To prevent XSS, developers can implement several techniques:

• Input Validation: Ensure that all input is validated against a set of rules.
• Output Encoding: Encode data before rendering it on the browser.
• Content Security Policy (CSP): Implement CSP to restrict resources that can be loaded.
• HTTPOnly and Secure Cookies: Use these flags to protect cookies from being accessed by JavaScript.
• Framework Security Features: Use built-in security features provided by web frameworks.

5.1 Use a Web Application Firewall (WAF)

Implement a WAF to filter and monitor HTTP traffic to and from your web application.

5.2 Regular Security Audits

Conduct regular security audits and code reviews to identify and fix vulnerabilities.

5.3 Use Security Libraries

Utilize libraries that automatically handle input sanitization and output encoding.