
Mozilla said that the new version fixes six security holes, one of which is rated 'critical'. Firefox 1.5 users are being offered an upgrade tool to move to the new browser.
"We anticipate this to be the last release in the Firefox 1.5.0.x series," said the Mozilla developers blog.
"Mozilla typically maintains support for previous releases for six months after a major release. Mozilla has previously extended the planned end of life for the 1.5.0.x series in order to accommodate some recent changes in update functionality."
The new browser contains one patch that covers 30 memory bugs in its JavaScript engines. The organisation also warned users of its Thunderbird email system that similar bugs could be found in the client.
"Thunderbird shares the browser engine with Firefox and could be vulnerable if JavaScript were to be enabled in mail," reads the security advisory.
"Some of these crashes showed evidence of memory corruption under certain circumstances and we presume that, with enough effort, at least some of these could be exploited to run arbitrary code."