Mozilla patched three critical vulnerabilities in Firefox 3.0 this week, including a Mac-specific bug reported by Apple, not just two as originally reported.

Firefox 3.0.1, the first update to the browser since it launched a month ago, fixed the same two flaws that were patched Tuesday in the older version 2.0.0.16, said Mozilla, but also quashed a Mac OS X-only vulnerability reported to the company by Drew Yao, an engineer in Apple's security group.

Last month, Yao had reported multiple bugs in Ruby, the object-oriented scripting language, to the open-source project. Apple patched those vulnerabilities in its own Mac OS X in late June.

A bug in how Firefox processes GIF-format images could be used by attackers to crash the browser, said Mozilla's security advisory, and "potentially execute arbitrary code." Firefox 2.0 is not affected, Mozilla said.

Details of the bug, however, were not publicly available on Bugzilla, Mozilla's bug tracking and management system.

Firefox 3.0.1, which Mozilla released Wednesday afternoon, also addressed several stability issues, fixed a problem with the anti-phishing/anti-malware blacklist, and took care of a printing problem.

Users can download Firefox 3.0.1 for Windows, Mac OS X and Linux from the Mozilla site, call up the browser's built-in updater or wait for the automatic update notification, which typically appears within 24 to 48 hours.