Individual skill
testing-for-xss-vulnerabilities
Tests web applications for Cross-Site Scripting (XSS) vulnerabilities by injecting JavaScript payloads into reflected, stored, and DOM-based contexts to demonstrate client-side code execution, session hijacking, and user impersonation. The tester identifies all injection points and output contexts, crafts context-appropriate payloads, and bypasses sanitization and CSP protections. Activates for requests involving XSS testing, cross-site scripting assessment, client-side injection testing, or JavaScript injection vulnerability testing.
internal/tools/skills/data/penetration-testing/testing-for-xss-vulnerabilities/SKILL.md
Source commit d42f381ad34843e71a42658e5c57290c713e85af
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- Matches the observed repository HEAD
- Yes
- Scanner rules are current
- Yes
- Repository scan complete
- No
- Skill scan complete
- No
- Observed behavior
- Network or broad shell
- Last checked
- Nov 9, 2026
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Repository context
- Repository stars (not skill ratings)
- 1,327
- Repository last updated
- Nov 9, 2026
- License
- Apache-2.0
Observed agent integration: No specific integration evidence. Standard SKILL.md installation does not imply verified compatibility.
- cybersecurity Repository topic
- security Repository topic
- bug-bounty Repository topic
- automation Repository topic
- autonomous-pentesting Repository topic
- ai-agent Repository topic
- ai-security Repository topic
- ethical-hacking Repository topic
- golang Repository topic
- penetration-testing Repository topic
- xss Declared skill tag
- cross-site-scripting Declared skill tag
- client-side-security Declared skill tag
- owasp-a03 Declared skill tag
- javascript-injection Declared skill tag
- security Derived category
- testing Derived category
- security-application Derived category
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# 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.
## Most Often Missed & How to Confirm
- **Output context, not just `<script>alert(1)`** — payloads must match where input lands (HTML body vs attribute vs JS string vs URL/`href` vs CSS). Testers who fire one body-context payload miss attribute breakouts (`" onfocus=alert(1) autofocus`), `javascript:` URIs, and JS-string escapes (`';alert(1)//`).