A security weakness in the update mechanism for third-party add-ons to the Firefox browser could give an attacker the ability to exploit unsecured downloads and install malicious code on the victim's computer, a security researcher warned on Wednesday.
The vulnerability affects any third-party add-ons that use an unsecured download site as part of the update process, according to Indiana University graduate student Christopher Soghoian, who released an advisory on the issue Wednesday.
While using the standard secure communications protocol available in major browsers, known as secure sockets layer (SSL) encryption, could prevent the attacks, many major companies - such as Google, Yahoo!, Facebook, LinkedIn, and AOL - failed to do so, Soghoian said.
"Many companies have world-class in-house security teams, so their worst sin is not consulting their own experts, who would have undoubtedly shot down any attempt to update code over an insecure and untrustworthy connection," Soghoian said in an email interview with SecurityFocus.
Soghoian, who attracted the attention of the US Department of Homeland Security last year when he created an online boarding-pass generator, posted an advisory and video of the attack to his website on Wednesday, a month and a half after notifying Mozilla and Google of the issue.
Vulnerability researchers have increasingly targeted Firefox as the open-source browser's popularity has grown. The group improved the browser's security with its latest version, Firefox 2.0, released last October. Both Microsoft and Mozilla have argued that their own browser protects internet users better.
In April, Soghoian decided to use a network sniffer to capture the data that Firefox sent out over the network as it was starting up. He quickly noticed that several extensions sent requests to check for new updates using plain Hypertext Transfer Protocol (HTTP) packets, without any sort of security.
"The insecure update requests stuck out like a sore thumb, and within a couple of hours, I had a working demo which proved that it was possible to hijack the extension upgrade process," Soghoian said.
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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