Firefox 18.104.22.168 was released earlier today. Must users will get the automatic update notification in the next 24-48 hours. However you can manually download and install the new version by going to getfirefox.com or simply selecting “Check for Updates…” from the Help menu. Several bug and security fixes are included in this version, see the complete Firefox 22.214.171.124 Release Notes
Attention Firefox 1.5 Users: In case you haven’t noticed Mozilla has ended support for this version of Firefox back in May 2007 and you really should be using the newer Firefox 2.0 builds.
News Source: Mozilla Developers News