Mozilla fixes 10 Firefox flaws, 5 critical

Through its updated version of its open-source browser, Mozilla has patched 10 vulnerabilities, half of which were marked as 'critical'.


Mozilla has patched 10 vulnerabilities in Firefox, half of which were marked as 'critical'.

The new Mozilla Messaging spin-off, however, was not able to provide a matching update to its Thunderbird email client, which shares five of the Firefox flaws that were fixed.

Mozilla's six advisories marked five Firefox bugs as 'critical', three as 'high' and one each 'moderate' and 'low'.

"There's a little bit here to interest everyone," said Andrew Storms, director of security operations at nCircle Network Security. "The bulletins claim no favour in the many types of vulnerabilities typically associated with browsers."

Among the critical flaws were a pair that could be exploited to crash Firefox or its JavaScript engine, and perhaps do more.

"Some of these crashes showed evidence of memory corruption under certain circumstances and we presume that with enough effort at least some of these could be exploited to run arbitrary code," Mozilla wrote in the advisory.

Mozilla also patched potential identity leaks, spoofing bugs and cross-site scripting vulnerabilities in But the fix that caught Storms' eye was a patch for LiveConnect, a feature that harks back to Firefox's predecessor, Netscape Navigator. LiveConnect lets Java applets call a web page's embedded JavaScript, or JavaScript access the Java runtime libraries, and is used by both Firefox and Apple's Safari 3.

"Sun has updated the Java Runtime Environment with a fix for this problem. Mozilla has also added a fix to LiveConnect to protect users who don't have the latest version of Java," Mozilla said in the advisory.

"Here we have Firefox putting out a mitigation step for a bug in Java," said Storms. "It's a welcomed addition when one vendor can help out another."

All 10 vulnerabilities were also patched by the SeaMonkey project, a separate open-source initiative that develops a multi-function browser suite.

The Thunderbird email client, meanwhile, is affected by the five critical flaws.

"Thunderbird shares the browser engine with Firefox and could be vulnerable if JavaScript were to be enabled in mail," read the first of the two bulletins. "This is not the default setting and we strongly discourage users from running JavaScript in mail."

A release date for Thunderbird to fix the flaws has not been set. According to David Ascher, the head of Mozilla Messaging, the emailer's update will follow Firefox's by "several weeks".

In a post to his blog last week, Ascher cited several reasons why a simultaneous release of Thunderbird and Firefox updates was impossible. "Some of those resource contentions are due to not enough automation for the Thunderbird release process, and some of it is the consequence of not enough people with the right training," he said.

Ascher defended the lag by noting that while JavaScript is turned on by default in Firefox, it is not in Thunderbird. "We could delay releasing Firefox until Thunderbird was ready, in the interest of mitigating the risk of someone using knowledge from the Firefox release to try and attack Thunderbird users," said Ascher. "But that would mean leaving over 150 million users vulnerable. So, applying the correct math, we release Firefox security updates as soon as possible, and Thunderbird security updates as soon as possible."

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