Users of Firefox 1.5 are advised to upgrade their browser by 24 April next year at the very latest, Mozilla said in a statement today.
The 220.127.116.11 update includes three critical security fixes for the open-source browser. Firefox users have already begun to receive the software through the browser's automatic update process.
The 24 April date means that Firefox 1.5 users are being given a six-month period to move over to the Firefox 2.0 browser, released last month.
Version 18.104.22.168 includes new software that allows Mozilla to push out Version 2.0 of the browser via Firefox's automatic update. The company could not confirm when a version of the browser would be available as an automatic update.
Mozilla developers are now debating on what to include in the Firefox 3.0 browser, which they hope to release one year from now. Anna Lagerkvist