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Amr Elsagaei’s JS Analysis Masterclass (Part 2) dives deep into JavaScript obfuscation, breakpoint debugging, and Chrome DevTools techniques for security researchers and bug hunters. The course is available here: JS Analysis Masterclass.
You Should Know:
1. JavaScript Obfuscation Techniques
Obfuscation is used to hide malicious code. Here’s how to deobfuscate it:
Using Browser Console to Deobfuscate
console.log(decodeURIComponent(escape(obfuscatedCode)));
Node.js Approach
const jsbeautifier = require('js-beautify');
console.log(jsbeautifier.js(obfuscatedCode));
2. Breakpoint Debugging in Chrome DevTools
Set breakpoints to analyze JS execution flow:
1. Open DevTools (F12 or Ctrl+Shift+I).
2. Go to Sources > Event Listener Breakpoints.
3. Enable Script First Statement or XHR/Fetch Breakpoints.
// Manually trigger a breakpoint debugger;
3. Bypassing Anti-Debugging Tricks
Many scripts detect DevTools. Disable detection with:
// Override debugger detection
window._debuggerHook = () => {};
Object.defineProperty(window, 'debugger', {get: () => false});
4. XSS Payload Analysis
Test potential XSS vectors using DevTools:
// Check if input is reflected unsanitized document.write(location.hash.slice(1));
5. Network Traffic Inspection
Monitor API calls for hidden vulnerabilities:
Use cURL to replicate requests
curl -X POST "https://target.com/api" -H "Cookie: session=123" --data-raw '{"user":"admin"}'
6. Automating JS Analysis
Use Puppeteer for dynamic analysis:
const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://target.com');
console.log(await page.content());
await browser.close();
})();
What Undercode Say
Mastering JavaScript analysis is crucial for uncovering security flaws in web apps. By combining breakpoints, deobfuscation, and DevTools tricks, researchers can dissect malicious scripts and uncover hidden attack vectors.
Expected Output:
- Deobfuscated JavaScript code.
- Identified XSS/SQLi vulnerabilities.
- Extracted API endpoints for further testing.
Prediction
As web apps grow more complex, advanced obfuscation and anti-debugging techniques will rise, requiring even more sophisticated analysis tools. Automated JS deobfuscation and AI-assisted code review may become standard in bug bounty workflows.
🔗 Course Link: JS Analysis Masterclass
References:
Reported By: Amrelsagaei Amrsec – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
