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🎯 PASTEBOARD XSS CHALLENGE - COMPLETE SUMMARY
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Challenge: https://pasteboard-1fb68b7836775bea.chals.uoftctf.org/
Bot: Runs Chrome with --no-sandbox --disable-gpu --headless flags

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✅ WHAT WE CONFIRMED WORKS
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1. XSS VULNERABILITY (CONFIRMED WORKING)
   - Location: app.js error handler
   - Method: DOM clobbering via <form id="errorReporter">
   - Payload structure:
     <form id="errorReporter"><input name="path" value="data:text/javascript,CODE"></form>
     <img id="renderConfig" src=x onerror="window.lastRenderError='x';throw new Error()">
   
   ✅ We successfully executed arbitrary JavaScript in bot's context
   ✅ Bot visits pages (confirmed via webhook requests)
   ✅ Can exfiltrate data via fetch() to external webhook

2. CONFIRMED DATA FROM BOT
   - Bot is running on localhost:5000
   - Bot is Chrome 143 on Linux (HeadlessChrome)
   - XSS executes successfully
   - User-Agent: HeadlessChrome/143.0.0.0

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❌ WHAT WE FOUND EMPTY/INACCESSIBLE
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1. STANDARD BROWSER APIS (All Empty)
   ❌ document.cookie → ""
   ❌ localStorage → empty
   ❌ sessionStorage → empty
   ❌ window.FLAG / window.flag → undefined
   ❌ No flag-related properties in window object

2. FILE/PROTOCOL ACCESS BLOCKED
   ❌ file:// protocol → NetworkError (blocked even with --no-sandbox)
   ❌ Tried fetch() to file:// URLs → Failed
   ❌ Tried navigation to file:// URLs → No response

3. INTERNAL ENDPOINTS (All 404)
   ❌ /flag, /flag.txt, /admin, /secret
   ❌ /static/flag.txt, /../flag.txt
   ❌ All returned 404 or no accessible data

4. CHROME DEVTOOLS PROTOCOL (CDP)
   ❌ localhost:9222/json → Connection failed (no debugging port)
   ❌ import('/devtools/main/main.js') → No response/silent failure
   ❌ chrome:// URL navigation → No response
   ❌ CDP Runtime.evaluate → Could not test (import failed)

5. TIMING/POLLING ATTEMPTS
   ❌ Polled for flag appearance for 20 seconds → nothing appeared
   ❌ Delayed checks (5-20 seconds) → no change
   ❌ No flag materialized asynchronously

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🔍 THE MYSTERY
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CONFIRMED FACTS:
1. bot.py defines: FLAG = "uoftctf{fake_flag}"
2. This FLAG variable is NEVER USED in the bot code
3. XSS works perfectly - we can execute arbitrary JS
4. --no-sandbox flag is present but CDP access doesn't work
5. Organizers said: "working as intended" and "solvable locally"

THE QUESTION:
WHERE IS THE FLAG ACTUALLY STORED/ACCESSIBLE?

Theories that DIDN'T work:
- Not in cookies (empty)
- Not in localStorage/sessionStorage (empty)
- Not in window global (checked all properties)
- Not in file system (file:// blocked, no accessible endpoints)
- Not via CDP (port not open, module import fails)
- Not set asynchronously (polling for 20 seconds found nothing)

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📋 COMPLETE LIST OF PAYLOADS TRIED
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1. Simple ping test → ✅ Confirmed XSS works
2. Comprehensive data dump → ✅ Got all browser data (all empty)
3. CDP exploitation (multiple variants) → ❌ No response
4. Chrome debugging port check → ❌ Port closed
5. DevTools module import → ❌ Silent failure
6. chrome://inspect navigation → ❌ No response
7. chrome://version navigation → ❌ No response
8. file:// URL fetch → ❌ Blocked
9. file:// URL navigation → ❌ No response
10. Internal endpoint scanning → ❌ All 404
11. Flag polling (20 seconds) → ❌ Nothing appeared
12. Delayed checks (5-10 seconds) → ❌ No change
13. Window property enumeration → ❌ No flag-related properties
14. HTML DOM search → ❌ No flag in page content
15. Meta tag search → ❌ No flag in meta tags
16. Hidden input search → ❌ No hidden flag inputs
17. CSS variable check → ❌ No flag in CSS
18. Performance entries check → ❌ No flag in timing data
19. Iframe source check → ❌ No iframes
20. Service worker check → ❌ No service workers

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💡 POSSIBLE MISSING PIECES
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1. REMOTE BOT MIGHT DIFFER FROM LOCAL
   - Maybe remote bot.py actually USES the FLAG variable
   - Maybe remote has different Chrome flags
   - Maybe remote has debugging port open

2. CDP ACCESS METHOD UNCLEAR
   - We couldn't get CDP to work
   - Maybe there's a different way to access it
   - ASIS CTF 2022 used CDP, but we can't replicate it

3. FLAG LOCATION UNKNOWN
   - Theory: FLAG is in process.env (Python environment variable)
   - Theory: FLAG is in a file we can't access without CDP
   - Theory: FLAG requires special Chrome flag we don't have
   - Theory: Remote challenge has different setup

4. POSSIBLE ALTERNATIVES NOT TRIED
   - Maybe there's a different XSS vector?
   - Maybe DOM clobbering can access something else?
   - Maybe there's a CSRF or other vulnerability?
   - Maybe need to exploit the bot differently?

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🛠️ TECHNICAL DETAILS FOR YOUR FRIEND
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XSS EXPLOIT MECHANISM:
1. app.js has error handler that loads script from window.errorReporter.path
2. We create <form id="errorReporter"> to clobber window.errorReporter
3. We set <input name="path" value="data:text/javascript,CODE">
4. We trigger error with <img onerror="throw new Error()">
5. Error handler loads our malicious script via data: URI
6. CSP allows this because of 'strict-dynamic' directive

BOT CONFIGURATION:
- Chrome 143 (HeadlessChrome)
- Flags: --no-sandbox --disable-gpu --headless
- Visits page for 30 seconds
- No cookies set before visiting
- No localStorage/sessionStorage set
- No debugging port open (localhost:9222 not accessible)

WHAT WE CAN DO:
✅ Execute arbitrary JavaScript in bot context
✅ Make fetch() requests to external servers
✅ Access all standard browser APIs
✅ Read DOM, document properties, window properties
✅ Navigate to URLs (though no response visible)

WHAT WE CANNOT DO:
❌ Access file:// protocol
❌ Access Chrome DevTools Protocol
❌ Navigate to chrome:// URLs (or at least see results)
❌ Find flag in any standard browser storage
❌ Access internal endpoints with flag

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❓ QUESTIONS FOR YOUR FRIEND
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1. How do we access the FLAG variable from bot.py in JavaScript?
   - It's defined but never used in the Python code
   - Is it supposed to be in process.env?
   - How do we read Python process environment from JS?

2. How do we get Chrome DevTools Protocol (CDP) access?
   - --no-sandbox should enable it, but how?
   - Import of /devtools/main/main.js fails silently
   - No debugging port open on localhost:9222
   - What are we missing?

3. Is there an alternative exploitation path?
   - Different vulnerability besides XSS?
   - Different way to access the flag?
   - Something we're overlooking in the source code?

4. Does the remote challenge differ from local?
   - Does remote bot.py actually SET a cookie with the flag?
   - Does remote have debugging port open?
   - Are there different Chrome flags on remote?

5. What does "solvable locally" mean exactly?
   - Same exploit works locally and remotely?
   - Or just the XSS part is testable locally?
   - Should we see the fake flag locally if we do it right?

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📁 FILES AVAILABLE
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All exploitation scripts created:
- quick_send.py → Sends simple ping test
- send_cdp.py → CDP exploitation attempt
- send_cdp_debug.py → CDP with step-by-step logging
- send_alternatives.py → Alternative methods
- auto_send.py → Interactive menu for all payloads
- TROUBLESHOOTING_GUIDE.txt → Complete troubleshooting steps
- README_CDP_SOLUTION.md → Full CDP exploitation documentation

Source code in src/:
- app.py → Flask application
- bot.py → Selenium bot (has FLAG variable that's never used)
- static/app.js → Contains XSS vulnerability
- templates/ → HTML templates

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🎯 BOTTOM LINE
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WE HAVE:
✅ Working XSS that executes in bot context
✅ Ability to exfiltrate any browser-accessible data
✅ Full control over JavaScript execution

WE'RE MISSING:
❌ Way to access the FLAG from bot.py
❌ Method to use Chrome DevTools Protocol
❌ Understanding of where flag is actually stored

THE EXPLOIT IS WORKING - WE JUST DON'T KNOW WHERE TO LOOK FOR THE FLAG.

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