Reverse Engineering Javascript
by viceCoolMan - Wednesday January 1, 2025 at 11:52 PM
#1
Why: By analyzing javascript files, you can uncover hidden parameters for API calls that automated tools might miss.
Example: I found an unauthenticated API call in lifeextension.com, by reviewing the Javascript, I found they required parameters to retrieve data.

How: To get started, you can use the Inspect Element or download all the JS files with an extension like Resource Saver. If you download the JS files, I recommend using a tool like waybackurls to passively find older files.

    Method .1: Search for XMLHttpRequest, "POST", and "GET" to find possible API calls. Any added parameters might be in the next lower lines.

    Method .2: If a function looks overwhelming, use Notepad and break the code down, line by line. It'll be less overwhelming and more manageable. 
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#2
There's an easier method. If you open the dev console and switch to network tab (activate preserve), you can see the api calls live while you browse the website. I'd do this first and if you can't find something, look in JS. But I'd always start with the easiest stuff first.
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