The best browser out there just became better.
Versions 18.104.22.168 for the Firefox 2 branch and 22.214.171.124 for the Firefox 1.5 branch are out. Update now!
And some news floating around says that 126.96.36.199 and 188.8.131.52 won’t be long either.
You may find a way to update Firefox manually using a .Mar file to be of use.