Moodle 2.7 Persistent XSS

Overview

I hope you all have heard about the Moodle project. The full form is Moodle Modular Object-Oriented Dynamic Learning Environment. This project is a free open-source project which focuses in teaching and learning online courses effectively. Most of the universities, colleges, educational institutes use this application in interacting with students. You can read and research more information on Wikipedia.

Vulnerability and Exploit

This is a persistent XSS I found in Moodle 2.7. Well, this vulnerability was present from the version 2.4.9 till 2.7 so far hidden from the eye 😉 luckily I spotted this while I was fuzzing random stuff against the application.

Edit your user profile and under “Optional” you can see “Skype ID”. Let’s inject some HTML into the Skype ID field and check the output

“>>><h1>Hello World</h1>

It seems like our input is echoed back thrice. In one line the input is being URL encoded since it should be the URL of the user and in another it is being converted to HTML entities, while in the other field it seems like our input is being filtered out. I love to break filters. Here is my quick and small analysis in detail.

Output 1:

<a href=”skype:%22%3E%3E%3EHello+World?call”>

Output 2:

&quot;&gt;&gt;&gt;Hello World

(more…)

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