Insecure plug-ins pose danger to Firefox users

Such requests could be intercepted by an attacker, if the victim used a wireless network or an untrusted wired network, he said. In particular, an attacker that had access to or control over the local domain name service (DNS) server could easily subvert the patch process. The attacker could then respond to the update request with a malicious add-on that could monitor the victim's internet connection and steal sensitive information.

The Mozilla Foundation acknowledged the issue, but stressed that any updates downloaded from its servers user SSL and are checked against a hash.

"We strongly recommend that add-on developers require SSL for updates to prevent the attack described above," Window Snyder, chief security officer for Mozilla, stated in a post to the group's developer blog.

The Mozilla Foundation released on Wednesday a patch for both version 1.5 and version 2.0 of the browser, fixing a critical memory corruption flaw.

Ironically, an amateur developer coding up a plug-in for Firefox will be much less likely to have to worry about the issue than a large company. Because most smaller developers use the Mozilla Foundation's Add-ons download site, they are more likely to be secure.

Google, for example, not only uses an unsecured connection to check for and download updates, but also suppresses any notification that an update is being installed, Soghoian said. The company has already created a patch and will automatically be updating Google Toolbar users soon, a representative said.

"We were notified of a potential vulnerability in some updates for Firefox extensions," the representative said in a statement sent to SecurityFocus. "A fix was developed for the Google extensions and users will be automatically updated with the patch shortly. We have received no reports that this vulnerability was exploited."

Soghoian, who spent last summer interning at Google, hopes that the search giant will also reconsider its decision to update users without notification. Firefox users now need to take a critical look at the third-party add-ons installed on their browser, and having as much information as possible helps, Soghoian said.

"As a matter of general policy, vendors really should not have their software silently install updates without asking the user's permission - it is asking for trouble," he stated in his advisory.

The Mozilla development team is currently considering ways that they could prevent insecure updates in the next version of the browser, Firefox 3.0, the group said on its blog.

This article originally appeared in Security Focus.

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