JavaScript Deobfuscation

🧠 Overview:

This module focused on understanding JavaScript obfuscation, why it’s used, and how to analyze obfuscated code during web assessments.

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🔎 Key Concepts:

🗂️ Where to Find JS Code:

• Inline in HTML (<script> tags)
• External files: Look for .js files in the page source or browser dev tools
• Network tab in dev tools or directory bruteforcing

🤐 What is Obfuscation?

• Process of making code difficult to read
• Commonly used to hide logic (e.g., login validation, token generation)
• Often used in malicious or poorly documented applications

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🔧 Tools to Deobfuscate:

• jsconsole.com
• prettier.io
• jsnice.org
• Browser Dev Tools (pretty print {} icon)

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🧪 Common Commands Used

Command	Description
curl http://SERVER_IP:PORT/	Basic GET request
curl -s http://SERVER_IP:PORT/ -X POST	Silent POST request
curl -s http://SERVER_IP:PORT/ -X POST -d "param1=sample"	POST with data
echo hackthebox \| base64	Base64 encode
echo ENCODED_B64 \| base64 -d	Base64 decode
echo hackthebox \| xxd -p	Hex encode
echo ENCODED_HEX \| xxd -p -r	Hex decode
echo hackthebox \| tr 'A-Za-z' 'N-ZA-Mn-za-m'	ROT13 encode
echo ENCODED_ROT13 \| tr 'A-Za-z' 'N-ZA-Mn-za-m'	ROT13 decode

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🧾 Summary:

This was a simple and fast module that introduced:

• How to spot and retrieve JS code
• How and why JavaScript is obfuscated
• How to deobfuscate and understand encoded logic
• Handy commands for decoding common encoding formats

Understanding JS obfuscation is critical for client-side validation bypass, logic analysis, and web exploitation.