Telescope 0.9.2 - Markdown Persistent Cross-Site Scripting

# Exploit Title: Persistent XSS via Markdown on Telescope  <= 0.9.2

# Date: Aug 22 2014

# Exploit Author: shubs

# Vendor Homepage: http://www.telescopeapp.org/

# Software Link: https://github.com/TelescopeJS/Telescope

# Version: <= 0.9.2

# CVE : CVE-2014-5144



Telescope 0.9.2 and below suffer from a persistent cross site scripting

vulnerability due to the lack of input sanitisation and validation

performed when parsing markdown user input. An authenticated user can

include links, images, code blocks and more through markdown, in the form

of comments, posts or replies and more.



As an example, the following vectors below can be used in comments, posts

or replies to trigger the XSS:



[notmalicious](javascript:window.onerror=alert;throw%20document.cookie)

[a](data:text/html;base64,PHNjcmlwdD5hbGVydCgnWFNTJyk8L3NjcmlwdD4K)



Once posted as comments, the above markdown is converted to links without

any sanitisation. When such links are clicked, the vector is executed

successfully.



Screenshots:

http://i.imgur.com/6SQgUYd.png

http://i.imgur.com/6VeZasj.png