This has been a crazy week of patching applications and the OS. First there was Microsoft's Patch Tuesday, then there was the Apple Quicktime update, and now Firefox. We are now in the age of zero-day exploits, so you need to move fast to protect yourself.
If you're using Firefox 1.5.x (and you have it automatically set to check for updates), then you should know by now that Firefox v18.104.22.168 has been released. If you have not upgraded already, then you should do it soon.
Here is a list of the fixes that are in this release. There are some features fixes, but most of them are security related.