While hunting for bugs on Main Web Apps, I encounter tons of interesting APIs. Some are well secured, obscurely documented, and keep you in your lane despite attempts to poke and prod. Others are surprisingly open and fully exposed via JavaScript files — making them much more interesting targets! Customized content enumeration, JavaScript file analysis, a keen eye, and some luck can net impactful results when it comes to exploiting APIs.

I’ve gathered some thoughts on how I recently found two impactful vulnerabilities in APIs, but the steps and techniques below should be generic enough to help find similar API…

Cross Site Scripting is a tricky bug to fix and bypasses for these fixes can be even trickier. While there are several ways to remediate or prevent XSS, I want to focus on HTML Entity Encoding and the contextual pitfalls that can occur with this method.

9 times out of 10, HTML entity encoding is going to block your attempts at popping an XSS. The app will render < > & " ' as HTML entities &lt; &gt; &amp; &quot; &apos;and make the reflected content safe and inert.

However, if you ever see this behavior occurring within a Javascript context…

Bend Theory

Hi! I'm Ben, a Web App Hacker, Bug Bounty Hunter, and Self-Taught Techno Entomologist

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