Mozilla has rushed out a new version of its browser to fix a crash bug that programmers inadvertently introduced. The fixed version comes just a week after the company last updated Firefox.

Firefox 3.5.5 repairs a small number of what the company called "stability issues" in the release notes that accompanied the update. Unlike almost all interim updates that Mozilla issues about once every six weeks, version 3.5.5 did not patch any security vulnerabilities.

The bug that has just been quashed was one that was causing a high number of crashes in the Windows version of Firefox 3.5.4, the update that Mozilla launched on 27 October to patch 16 flaws.

"We're seeing lots of crashes in the GIF decoder," noted Mozilla developer Joe Drew in the message that kicked off the discussion on Bugzilla, the company's bug and change tracking system. Only the Windows edition of Firefox 3.5.4 was crashing, others reported on Bugzilla. The GIF decoder is the component that parses .gif image files embedded in web pages.

"This bug was actually caused by bug 514776 which removed the check for null mImageFrame," said another Firefox programmer, Jeff Mulzelaar, on Bugzilla. "I don't know why that check was removed." Information about the bug Mulzelaar mentioned is password-protected and not available to the general public.

Firefox 3.5.5 also fixes a stability bug in the Mac version, and another crash problem in the Windows and Mac editions.

Mozilla's older browser, Firefox 3.0, was not affected by the bugs. The most up-to-date version of that edition is Firefox 3.0.15, which was also released 27 October.

Firefox accounts for an estimated 24 percent of all browsers worldwide, according to data from US web metrics company Net Applications.

Firefox 3.5.5 can be downloaded for Windows, Mac OS X and Linux from the Mozilla site; current Firefox users can call up the browser's update tool or wait for automatic update notifications to appear.