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Yoono Firefox Extension - Privileged Code Injection
From: Nick Freeman <nick.freeman () security-assessment com>
Date: Wed, 13 Jan 2010 23:05:04 +1300

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        \/         \/.-.    \/         \/:wq
                    (x.0)
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                  _='`"``=.

        presents..

Yoono Firefox Extension Code Injection Vulnerability
Versions affected: < 6.1.1


+-----------+
|Description|
+-----------+

The Yoono Firefox extension provides an interface for 
users to share objects with their friends on social 
networks from any website. It allows users to select 
images from a website to be shared, which publishes 
that image to their friends.

Security-Assessment.com discovered that Yoono's share 
function is vulnerable to DOM event handler injection.
The vulnerability affects the DOM event handlers of 
<img> tags which can be shared via Yoono.

Yoono's share function directly evaluates remotely 
supplied content, within the privileged chrome 
context. This can allow a malicious image on a 
website to exploit users who share it, and may lead 
to the complete compromise of the host.

    
+------------+
|Exploitation|
+------------+

This vulnerability can be exploited in several ways.
As the injection point is in the chrome privileged
browser zone, it is possible to bypass Same Origin
Policy (SOP) protections, and also access Mozilla
built-in XPCOM components. XPCOM components can be
used to read and write from the file system, as well
as execute arbitrary commands, steal stored passwords,
 or modify other Firefox extensions.


+--------+
|Solution|
+--------+

Security-Assessment.com follows responsible disclosure
and promptly contacted the developer after discovering
the issue. The developer was contacted on June 30,
2009, and a response was received on the same day. A 
fix was released on July 6, 2009.  

The vendor supplied patch is available
from Mozilla (https://addons.mozilla.org/en-US/firefox/addon/1833)
or from the developer’s website, http://www.yoono.com.


+------+
|Credit|
+------+

Discovered and advised to the Yoono developers
June 2009 by Nick Freeman of Security-Assessment.com.
Contact: Nick Freeman \\AT\\ security-assess\m/ent.com
Personal Page: http://atta.cked.me


For full details regarding this vulnerability
(including a detailed proof of concept exploit)
download the PDF from our website:
http://security-assessment.com/files/advisories/Yoono_Firefox_Extension_Privileged_Code_Injection.pdf

For more details regarding exploitation of Firefox
extensions, refer to our DEFCON 17 presentation at
http://security-assessment.com/files/presentations/liverani_freeman_abusing_firefox_extensions_defcon17.pdf.

Security-Assessment.com is a New Zealand based world
leader in web application testing, network security
and penetration testing. Security-Assessment.com
services organisations across New Zealand, Australia,
Asia Pacific, the United States and the United
Kingdom.



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