Mozilla yesterday patched 11 vulnerabilities in the desktop edition of Firefox as it upgraded the browser to version 7.
The company has batted a thousand so far in its rapid release schedule: Firefox 7 marks the third consecutive upgrade that Mozilla has met its every-six-week deadline for a new version of the browser.
Mozilla switched to the faster release tempo last March, when some wondered whether the open-source company -- which has historically struggled to ship on time -- would be able to make its milestones.
The biggest improvement to Firefox 7 is a reduction in memory use. Mozilla has previously claimed that the upgrade slashes memory consumption by as much as 50% .
"Firefox  manages memory more efficiently to deliver a nimble Web browsing experience," Mozilla said Tuesday when it launched the new edition. "Users will notice Firefox is faster at opening new tabs, clicking on menu items and buttons on websites."
Most users will see a 20%-to-30% reduction in memory usage compared to Firefox 4, Mozilla said, but in some situations that can climb to 50%.
In an accompanying blog post on the Firefox 7 memory changes, Mozilla said that Windows users will see the most benefit.
The company also claimed that the memory diet has boosted the browser's performance, especially in scenarios where users have opened numerous tabs and leave Firefox running for long stretches.
Firefox has long been knocked as hogging memory, criticism that prompted Mozilla to kick off the "MemShrink" project , which was designed to drive down Firefox's memory use and close "memory leaks" -- bugs that prevent memory from being released to the system when tabs are closed.
Other changes that debuted in Firefox 7 included a new hardware acceleration framework to speed up HTML5 rendering, and an opt-in tool called Telemetry that lets users send performance data to Mozilla.
Firefox 7 also patched 11 security vulnerabilities, 10 of which were rated "critical," the company's most serious threat rating; the sole exception was labeled "moderate."
Because Mozilla now bundles virtually security patches almost exclusively with each version upgrade, users stuck on Firefox 6 or earlier must update to quash the bugs.
Two of the critical vulnerabilities patched Tuesday were in Firefox's implementation of WebGL, a 3-D rendering standard that both Firefox and Google's Chrome comply with. One of the pair was reported to Mozilla by a researcher with Context Information Security, a company that has cited serious security issues with WebGL.
The other was credited to a member of Google's security team.
Firefox has received several patches specific to WebGL since Context recommended users and administrators disable the standard in Mozilla's browser and in Chrome.
Mozilla also released Firefox 3.6.23 yesterday, a security update that patched four vulnerabilities. That aging edition -- Mozilla first shipped Firefox 3.6 in January 2010 -- is still maintained, in part because enterprise users have resisted adopting the rapid release cadence.
As part of a proposal called Extended Support Release, Mozilla plans to halt Firefox 3.6 security updates three months after it kicks off a less-frequent shipping schedule for corporations.
Firefox 7 can be downloaded manually from Mozilla's site, while people running Firefox 4, 5 or 6 will be offered the upgrade through the browser's own update mechanism.
The next version of Firefox is currently scheduled for release on Nov. 8.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer , on Google+ or subscribe to Gregg's RSS feed . His e-mail address is email@example.com .
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