At the SecurityByte & OWASP AppSec Conference in India, Roberto Suggi Liverani and Nick Freeman, security consultants with security-assessment.com, offered insight into the substantial danger posed by Firefox extensions.
Mozilla doesn't have a security model for extensions and Firefox fully trusts the code of the extensions. There are no security boundaries between extensions and, to make things even worse, an extension can silently modify another extension.
Any Mozilla application with the extension system is vulnerable to same type of issues. Extensions vulnerabilities are platform independent, and can result in full system compromise.
The researchers believe that the weakest link in the chain is the human factor. Many add-on developers do it for a hobby and are not necessarily aware of how dangerous a vulnerable extension can be. The extension reviewers don't need to have great knowledge about Web application security and follow guidelines on finding malicious extensions. This means vulnerable extensions can easily slip through.
Researchers have found several bugs in popular Firefox extensions that have an estimate total amount of 30 million downloads from AMO (Addons Mozilla community site). Three 0days were also released at the SecurityByte & Owasp AppSec Asia 2009 conference.
Sage 1.4.3 and previous
When you click on a malicious feed, it changes your NoScript settings and introduces the website in question on the whitelist of websites that are allowed to execute scripts.
InfoRSS 126.96.36.199 and previous
Yoono 6.1.0 and previous
Yoono is free software that allows you to connect and share with all your social networks and instant messaging services in one place. By using this extension, users can quickly save and share images from other web sites.
The problem here is that when using the extension on a malicious web site, remote file can be automatically downloaded and executed on your machine. Reverse VNC is just one of the options that can lead to the full compromise.
Speaking for Help Net Security, security researcher Roberto Suggi Liverani discusses his findings:
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