The latest in the line of updates that have rolled off the Mozilla development line every six weeks since mid-2011, Firefox 12 fixed seven vulnerabilities labeled "critical," the highest threat ranking in Mozilla's four-step scoring, four bugs tagged "high" and three pegged "moderate."
Mozilla also patched 19 other bugs, all critical, in the mobile edition of Firefox, which runs on the Android platform.
Among the 14 desktop vulnerabilities, Mozilla patched three that could be used by hackers in cross-site scripting (XSS) attacks, one that applied only to Windows Vista and Windows 7 PCs with hardware acceleration disabled and another in image rendering done by the WebGL 3D standard.
Two of the bugs were reported by security researchers at rivals Google and Opera Software. The Google engineer also notified Mozilla of all 19 vulnerabilities in the FreeType library that affected the mobile version of the browser.
Unlike Google, Mozilla does not call out bounties it's paid to outside researchers for reporting vulnerabilities, even though Mozilla does have a reward program.
As usual, Mozilla did not explicitly say that all the flaws could be exploited, but instead hedged with its traditional phrasing of, "We presume that with enough effort at least some of these could be exploited to run arbitrary code."
Eleven of the 14 bugs were also patched in Firefox ESR, or Extended Support Release, the longer-lived edition designed for enterprises that don't want to update workers' machines every few weeks.
The current version of Firefox ESR is based on Firefox 10, which shipped in December 2011. ESR receives only security updates during its 54-week lifespan. The first iteration of ESR won't appreciably change until November 2012, and will be supported with security patches until early February 2013.
As expected, Mozilla did not release fixes for Firefox 3.6, the 2010 browser it officially .
Mozilla has been nagging Firefox 3.6 users with pleas to upgrade for weeks, and will take the unusual step of automatically upgrading them to Firefox 12 early next month.
Although Mozilla touted a total of 85 improvements for Web developers, it focused on the feature that brought the browser, at least on Windows, one step closer to true "silent" updating.
Firefox 12 skirts Windows' UAC prompt, but by clearing the highlighted box, users can restore the warning.
"Firefox simplifies the update process for Windows users by removing the user account control dialog (UAC) pop-up while maintaining the security of your system," the company said in a announcing the release of Firefox 12. "Once a user gives explicit permission to Firefox on their first installation, they will not be prompted again for subsequent releases."
pushes Firefox updates further into the background on Windows Vista and Windows 7 machines; both operating system demand users' approval before installing software.
While updating Firefox to version 12 requires a click in the UAC dialog on Vista and Windows 7, that should be the last time users see the prompt.
Users can restore UAC's interruption to Firefox updates if they wish by clearing a box in the "Advanced" section of the Options window.
Mozilla has just one more component on its silent update to-do list.
That piece, now scheduled to appear in either Firefox 13, which ships June 5, or Firefox 14, slated to release July 17, will apply the update entirely in the background so that the user no longer sees an update installation progress bar.
Called "background updating" by Mozilla, the process will seem invisible to users because the update is automatically applied, then staged in a different directory or folder than the current copy of the browser. The next time Firefox is launched, the staged directory swaps places with the active directory.
Mozilla has been chasing Google's Chrome, which has featured silent, behind-the-scenes updating, since the latter's 2008 debut.
The open-source developer has been working on silent updating for nearly two years. At one point, it thought it could add the feature to Firefox 4, which shipped in March 2011, but the company abandoned work when that version was delayed several times for other reasons. And late last year, Mozilla said it was shooting for silent updating in Firefox 10, which debuted in January 2012. Those plans were also scrapped.
Windows, Mac and Linux editions of can be downloaded manually from Mozilla's site. Users running Firefox 4 or later will be offered the upgrade through the browser's own update mechanism.
The next version of Firefox is scheduled to ship June 5.
in Computerworld's Browsers Topic Center.