Mozilla has updated versions 2 and 3 of its Firefox Web browser to fix a pair of security vulnerabilities.

Firefox version 2.0.0.16, released on Tuesday, and Firefox 3.01, released on Wednesday, address MFSA 2008-35, a flaw that allows command-line URLs to launch multiple tabs when Firefox is not running, and MFSA 2008-34, a flaw that could allow remote code execution as a consequence of a CSS reference counter overflow.

MFSA 2008-35 could potentially be exploited using what has some to be known as the "Safari Carpet Bomb" attack, a combined attack technique reported for the Windows version of Apple's Safari Web browser in May.

The MFSA 2008-35 vulnerability could be used to execute remote code on a Firefox 2 user's machine and is considered critical. Firefox 3 users are better protected, and would likely face a less serious attack like spoofing, unless the attack was combined with some means of privilege elevation.

Earlier this month, researchers from ETH Zurich, Google, and IBM published research showing that 637 million (45.2%) out of 1.4 billion Internet users worldwide are at risk from their failure to use the latest, most secure version of their chosen Internet browser.

Among the various Web browsers studied -- Internet Explorer 7, Firefox 2, Safari 3, and Opera 9 -- Firefox 2 was deemed the most secure, according to the study, because 83.3% of its users worldwide are running the most current version.

Firefox 3 was released on June 17, 2008 and wasn't considered in the study. Thanks to the evangelism of Mozilla and its supporters, Firefox 3 set a world record for the most downloads in a 24 hour period (8,002,530) on July 2, 2008.