Three bugs have been patched by the Mozilla team - one of which could have left Mac users open to hack attacks.
The Firefox 3.0.1 patches three critical vulnerabilities in Firefox 3.0.
These included a Mac-specific bug reported by Apple, which it suggested could leave Firefox users vulnerable to cyber crime.
A bug is caused by a fault in how Firefox processes GIF images, and Mozilla explained that this could be used by attackers to crash the browser.
Firefox 2.0 is not affected, it added.
Firefox 3.0.1 is the first update to the browser since it launched a month ago.
It also addressed several stability issues, fixed a problem with the anti-phishing/anti-malware blacklist, and mended a printing problem.
Users can download Firefox 3.0.1 for Windows, Mac OS X and Linux from the Mozilla site.