Identifying XSS Types in Practice

Distinguishing between XSS types is crucial for both attack detection and prevention. Reflected XSS typically appears in server responses immediately after user input, often visible in URLs or form submissions. Stored XSS payloads persist in databases or files and affect multiple users over time. DOM-based XSS operates entirely on the client side, often involving JavaScript functions that handle user input unsafely. Security teams can identify reflected XSS through input/output analysis, stored XSS through database content scanning, and DOM-based XSS through JavaScript code review and dynamic analysis tools.

Understanding these XSS variants enables developers to implement appropriate defenses. While output encoding helps prevent reflected and stored XSS, DOM-based XSS requires secure JavaScript coding practices. Content Security Policy headers can mitigate all types but must be configured correctly for each application's needs. As web applications continue to evolve, new XSS variants may emerge, but understanding these fundamental types provides the foundation for recognizing and preventing future attacks. The key is to treat all user input as potentially malicious and implement defense-in-depth strategies appropriate to each XSS type.