Configuring ZAP for Optimal XSS Detection

Effective XSS detection begins with proper scan policy configuration. Create a dedicated XSS testing policy through Analyse > Scan Policy Manager. Enable all XSS-related rules: "Cross Site Scripting (Reflected)," "Cross Site Scripting (Persistent)," "DOM Based Cross Site Scripting," and related variants. Set these rules to HIGH strength for comprehensive testing, though this increases scan duration significantly.

Context configuration dramatically improves XSS detection accuracy. Define URL parameters, form fields, and headers that accept user input. Configure input vectors to use appropriate data types—text fields need different payloads than numeric inputs. Enable anti-CSRF token handling for applications using token protection. Proper context configuration prevents false negatives from application errors rejecting malformed input.

# XSS Scan Policy Configuration
Cross Site Scripting (Reflected): Enabled, Strength: High, Threshold: Low
Cross Site Scripting (Persistent): Enabled, Strength: High, Threshold: Medium  
DOM Based Cross Site Scripting: Enabled, Strength: Medium
Cross Site Scripting (Reflected - Server Side): Enabled, Strength: High
Cross Site Scripting (Persistent - Server Side): Enabled, Strength: Medium

# Additional Related Rules
Client Side Resource Manipulation: Enabled
External Redirect: Enabled
Anti-CSRF Tokens Check: Enabled

Browser configuration impacts XSS detection, especially for DOM-based variants. Use ZAP's browser launch features to ensure consistent testing environments. Disable browser XSS filters during testing to prevent interference with detection. Modern browsers include various security features that might block XSS exploitation but not the underlying vulnerability. Testing with security features disabled reveals true application security posture.