Feed Sidebar Firefox Extension - Privileged Code Injection

Type securityvulns
Reporter Securityvulns
Modified 2009-08-25T00:00:00


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Feed Sidebar Firefox Extension Code Injection Vulnerability Versions affected: < 3.2

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

The Feed Sidebar Firefox extension will generate a preview of any RSS item, from feeds you have currently subscribed to. Security-Assessment.com discovered that Feed Sidebar is vulnerable to multiple injection vulnerabilities which can be exploited through a malicious RSS feed. Cross-Site Scripting and HTML injection vulnerabilities were discovered within the RSS <description> tags of subscribed feeds.

Feed Sidebar directly evaluates remotely supplied content, within the privileged chrome context. This occurs when a user clicks on a feed item in the Feed Sidebar, rendering a preview of the feed item at the bottom of the sidebar. This can allow a remote feed to exploit users browsing 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 March 4, 2009, and a response was received on the following day. A fix was released on March 14, 2009.

The vendor supplied patch is available from Mozilla (https://addons.mozilla.org/en-US/firefox/addon/4869) or from the developer’s personal website,

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

Discovered and advised to the Feed Sidebar developer March 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/Feed_Sidebar_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.