"Even before shipping the RC, we've managed to find a number of issues that needed fixing," said Mike Beltzner, the director of Firefox.
The web browser was initially set for release in the first week of June. However it now looks likely that the browser won't be made available until June 10 at the earliest.
Beltzner attributed the bug finds to a "newfound rigor" in testing, as well as a larger number of users hammering on the RC code. "[All this] makes it easier for us to spot potential problems with a milestone much earlier than ever before," he said.
Last year, Mozilla delivered the final release candidate of Firefox 3.0 on June 4, then launched the browser two weeks later, on June 17. Assuming it meets that same timeline this year, Mozilla could ship Firefox 3.5 by June 25 if it sticks to just one RC and drops that on users by June 12.
Firefox currently accounts for 22.5% of the browser market, according to web metrics company Net Applications' most-recent data. But it faces renewed competition on almost every front, including Microsoft and its Internet Explorer 8, Google's Chrome browser, and even Opera Software, which launched a public beta of Opera 10 yesterday.
Firefox 3.5 is the new moniker by which Firefox 3.1 goes by. Mozilla changed the browser's name earlier this year after developers said '3.1' didn't properly reflect the amount of new features and changes from last June's Firefox 3.0.