Mozilla has delivered the final version of Firefox 5, the first edition under the new faster-release regime it kicked off earlier this year.
The company also patched 10 bugs in Firefox 5, including one in the browser's handling of the WebGL 3-D rendering standard that rival Microsoft has called unsafe.
Firefox 5 met Mozilla's self-imposed deadline of June 21, notable because the company has historically struggled to ship browser upgrades on time.
Firefox 5 looks identical to its predecessor, Firefox 4, but Mozilla's made changes under the hood.
Shortly after Mozilla launched Firefox 4 in March, the company committed to a faster release schedule that puts the browser on a six-week refresh cycle that lets developers add features as they're completed, rather than hold them until all work on the next upgrade is completed. If a feature presents problems, it's yanked and re-inserted into a later cycle after fixes have been applied.
Mozilla has denied copying Google Chrome's upbeat schedule -- that browser was the first to institute a fast-release strategy -- but analysts have noted the similarities and pointed out the need of all browser makers to step up the pace.
Because of the shorter development cycle, Mozilla called out relatively few new features in Firefox 5.
Although the company said it added more than 1,000 improvements to the browser, most were minor bug fixes or tweaks. Among the most significant changes were enhanced support for HTML5 and new support for CSS (cascading style sheet) animations.
Firefox 5's user interface is nearly identical to Firefox 4, for instance.
Mozilla also dropped a feature it had touted during the testing phase, dumping a tool that let users change development channels from, say, the final to either Beta or Aurora, rougher builds that precede the most stable edition. The company decided that few were using the channel switcher, and rather than devote time and resources to maintaining the feature, pulled it.
Mozilla did not make a major marketing push for Firefox 5, another departure from past upgrades when it has touted the number of downloads and gotten supporters to throw release parties.
On the security front, Mozilla patched vulnerabilities in both Firefox 3.6 and Firefox 5.
Ten of the 11 bugs fixed in Firefox 3.6, which Mozilla said it will continue to support "for a short amount of time," were rated "critical," the company's most serious threat rating; the one exception was tagged as "moderate."
Seven of the 10 bugs quashed in Firefox 5 were also rated critical, two were labeled moderate and the last was pegged a "low" threat.
One of the moderate vulnerabilities patched in Firefox 5 was in the browser's implementation of WebGL , a 3-D rendering standard that both Chrome and Firefox rely on. The bug was reported to Mozilla by Context Information Security, which has cited several serious security issues with WebGL, including information theft.
Context has recommended that users and administrators disable WebGL in Chrome and Firefox.
Microsoft, whose Internet Explorer 9 (IE9) does not support WebGL, has gone further in its criticism of WebGL, and by association, its biggest rivals. "Customers need to understand that the security of their computers is at risk when they browse the Web using Google Chrome and Firefox," Ari Bixhorn, director of IE, said in a statement on Friday.
IE's usage share has eroded under pressure from rivals Mozilla and Google. Microsoft's browser has lost users to Firefox and more recently, Chrome, as first one and then the other gained share at IE's expense. As of the end of May, IE's global share was 54%, down from over 90% in 2004.
Over the last year, IE has lost about half a percentage point of share each month, with the bulk of it going to Chrome.
Users running Firefox 4 will be offered the upgrade to Firefox 5 through the browser's update mechanism, which is triggered when the "About Firefox" dialog is opened. In Windows, users can select "Help/About Firefox" from the Firefox button at the upper left of the browser Windows. On a Mac, "About Firefox" is the first choice under the Firefox menu.
Firefox 5 can also be downloaded manually from Mozilla's site.
The next version of Firefox is currently on schedule for an early August release.