Mozilla has released Firefox 3.0.4, the fourth update to Firefox 3, released last June.
As usual, this release brings several stability and performance bug fixes, as well as, according to the release notes, some security patches. Details of the security vulnerabilities have not been disclosed as of this post.
Also notable in this release is the availability of two new languages: Icelandic and Thai. Bulgarian, Esperanto, Estonian, Latvian, Occitan, and Welsh are also in the works and available for general testing.
To update, select Check for Updates… in the Help menu and follow the onscreen instructions.
Note that if you are using a firewall it will most likely require your approval to let the updated Firefox access the Internet. For more information, check Cannot connect after upgrading Firefox at Mozilla Support Knowledge Base (uh, before updating).
Update: Security fixes details available now: 4 critical, 2 high, 2 moderate, and 1 low impact. Update now.