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Discovering hidden JavaScript (JS) endpoints can lead to critical vulnerabilities, as demonstrated by a researcher who earned $7,000 from Pinterest’s Bug Bounty program. By analyzing JS files, attackers (or ethical hackers) can uncover undocumented API endpoints that may expose sensitive user data.
How to Find Hidden JS Endpoints in Chrome
1. Open Chrome DevTools (`Ctrl+Shift+I` or `F12`).
2. Navigate to the Sources or Network tab.
- Search for `.js` files in the Page or XHR/fetch requests.
4. Use `Ctrl+F` to search for keywords like:
– `api/`
– `endpoint`
– `fetch(`
– `axios.get(`
– `userData`
5. Manually test discovered endpoints for misconfigurations (IDOR, excessive data exposure).
Automating the Process
Use tools like:
- Burp Suite (Passive Scanner)
- LinkFinder (
python3 linkfinder.py -i https://example.com -o results.html) - JS-Scan (`npx js-scanner https://example.com`)
You Should Know: Practical Commands & Techniques
Linux Command for JS Endpoint Extraction
curl -s https://example.com/file.js | grep -Eo "(http|https)://[a-zA-Z0-9./?=_%:-]" | sort -u
Windows PowerShell Alternative
(Invoke-WebRequest -Uri "https://example.com/file.js").Content | Select-String -Pattern "https?://[^\s\"']+" -AllMatches | % { $_.Matches.Value } | Sort-Object -Unique
Using `ffuf` for Endpoint Fuzzing
ffuf -w /path/to/wordlist.txt -u https://example.com/FUZZ -mc 200,403
What Undercode Say
Hidden JS endpoints remain a goldmine for bug hunters. Many companies overlook internal API routes exposed in client-side scripts, leading to data leaks, authentication flaws, and broken access control. Always:
– Review minified JS using beautifiers like jsbeautifier.org.
– Monitor AJAX calls in the Network tab.
– Automate recon with tools like SecretFinder (python3 SecretFinder.py -i target.com -o output.txt).
Prediction
As companies shift toward single-page applications (SPAs), JS endpoint exposure will increase, making this technique even more valuable for bug bounty hunters.
Expected Output:
A list of exposed API endpoints, misconfigured internal routes, or sensitive data leaks from JS files.
Reference:
References:
Reported By: Priyanshu Shakya – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
