Testing Methodologies for Different XSS Types

Each type of XSS requires specific testing approaches. For reflected XSS, focus on immediate input-output relationships. Test every URL parameter, form field, and header that might be reflected in the response. Use unique markers in payloads to track where input appears in the output. For example, injecting XSS123TEST helps identify all reflection points before crafting specific exploits. Test both GET and POST requests, as applications might handle them differently.

Stored XSS testing requires patience and systematic tracking. Create test accounts to isolate your payloads and avoid affecting real users. Document where each payload is injected and where it might be displayed – user profiles, comments, messages, logs, or administrative interfaces. Some stored XSS vulnerabilities have delayed execution, appearing only under specific conditions or to certain user roles. Use time-delayed payloads or callbacks to detect when stored payloads execute, especially in areas you can't directly access.

DOM-based XSS testing demands understanding JavaScript code flow. Start by identifying sources (where attacker-controlled data enters JavaScript) and sinks (where this data is used dangerously). Common sources include location.href, document.referrer, and postMessage events. Dangerous sinks include innerHTML, document.write, and eval. Modern browsers' developer tools allow setting breakpoints on these functions to trace data flow. Testing involves manipulating source data and observing if it reaches dangerous sinks without sanitization.