Mozilla Releases Firefox 3.5.7

Mozilla is out with the first update of 2010 to its open source Firefox Web browser. Unlike its immediate predecessor, Firefox 3.5.7 is not being issued to fix security issues, but rather is an update for a trio of stability-related bugs.

The fixed bug list for Firefox 3.5.7 includes one flaw classified as critical and two as major by Mozilla. The critical flaw is a fix for what Mozilla has labeled as a Topcrasher on Windows for Firefox 3.5.x. The flaw was first reported last July and carries the official bug title of, “[Win] Topcrasher for Firefox 3.5.1 [@ memmove | nsTArray_base::ShiftData(unsigned int, unsigned int, unsigned int, unsigned int)][@ nsObserverList::FillObserverArray]” (

The crash condition could potentially cause Firefox to shut down unexpectedly on a number of popular Web sites.

“I suspect URLs aren’t going to help much on this bug,” Mozilla developer Chris Hoffman wrote in a bugzilla entry. “There seems to be a wide distribution of time to crash with the average crash taking longer than 2 hours, a wide variety of versions, and the sites where the crash is seen is pretty much reflective of general Web surfing.”

Among the major fixes for Firefox 3.5.7 is one that is intended to help users get major updates for Firefox. Mozilla has two principal types of updates for Firefox, major and minor. The minor releases are often the point releases, such as Firefox 3.5.7. The last major Firefox update was the Firefox 3.5 update, which was made available to Firefox 3.0.x users. The problem identified by Mozilla developers was that not enough Firefox users were updated through the prompted major update mechanism.

“Our prompted major update (PMU) isn’t getting good uptake,” Mozilla developer Sam Sidler wrote in a bugzilla entry. “The last one we had also didn’t do as well as in the 2.0.0.x -> 3.0.x days. We attributed this to the timing of that update, but in this case, we’ve only see about 1m people accept the major update, well below expectations and well below what has happened in every other major update (usually it’s as low as 10%).”

With 3.5.7, Mozilla is aiming to improve the update system in order to get better uptake for its next major update.

Mozilla developers are now working on Firefox 3.6 with the first Release Candidate builds being made available this week. Firefox 3.6 includes new performance enhancements and security improvements. It will also mark the debut of machine orientation in Firefox, so the browser will be able to take advantage of hardware features to adjust the screen based on the orientation (vertical, horizontal, etc.) of the physical device the browser is running on.

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