Mozilla has released the next version of Firefox 3.6 on Tuesday, January 31st. Firefox 3.6.26 fixed several security issues and stability issues.
Existing Firefox 3.6.x users should be prompted for an update within the next 24-48 hours. However, users may be able to update manually from within Firefox via Help > About Firefox. User can also manually download and install Firefox 3.6.26 here.
The next scheduled Firefox release is Firefox 3.6.27 set for Tuesday, March 13, 2012. The final update for Firefox 3.6 will be Firefox 3.6.28 on April 24th, 2012.