Mozilla is rushing out a new release of Firefox, fixing critical security vulnerabilities in the software and, for the first time, checks to see if the browser's Flash Player is up-to-date.

The Firefox 3.5.3 and 3.0.14 updates were released just a day after Microsoft pushed out its monthly set of security patches. The updates come two months after Firefox 3.5 was launched.

By actively checking for up-to-date Flash software, Mozilla hopes to give users a smoother, and more secure, web browsing experience. Mozilla decided to focus on the Flash Player "both because of its popularity and because some studies have shown that as many as 80 percent of users currently have an out of date version," said Mozilla spokesman Johnathan Nightingale in a recent blog on the issue. "Mozilla will work with other plugin vendors to provide similar checks for their products in the future," he added.

Computer criminals have increasingly turned to bugs in add-on software such as Flash and QuickTime as they look for new ways to hack into PCs.

The three critical bugs that were patched yesterday lie in internal Firefox components. They are considered critical, because Mozilla developers think that hackers could leverage them to overwrite parts of the computer's memory and eventually run unauthorised software on the victim's PC.

Two other bugs were patched on Wednesday, but Mozilla rates them both as lower security risks.