Testing for XSS Vulnerabilities

When to Use

• Testing web applications for client-side injection vulnerabilities as part of OWASP WSTG testing
• Evaluating the effectiveness of input sanitization and output encoding across all application features
• Assessing the protection provided by Content Security Policy (CSP) headers against XSS exploitation
• Demonstrating the impact of XSS through session hijacking, credential theft, or phishing overlay to stakeholders
• Testing single-page applications (React, Angular, Vue) for DOM-based XSS in client-side routing and rendering

Do not use against applications without written authorization, for deploying persistent XSS payloads that affect real users, or for exfiltrating actual user session tokens from production environments.

Prerequisites

• Authorized scope defining the target web application and acceptable testing activities
• Burp Suite Professional with XSS-focused extensions (XSS Validator, Reflector, Active Scan++)
• Browser with developer tools and XSS testing extensions (HackBar, XSS Hunter)
• XSS Hunter or Burp Collaborator for out-of-band payload verification
• SecLists XSS payload lists and custom payloads for WAF bypass scenarios