Mozilla has issued updated versions of  Firefox, Thunderbird and Seamonkey with fixes for multiple vulnerabilities. Descriptions of the vulnerabilities that were addressed with this update can be read at;
Firefox 1.5.0.7 Release notes
Thunderbird 1.5.0.7 Release notes
SeaMonkey 1.0.5 Release notes

Downloads for these updated Mozilla products are at Firefox Thunderbird and SeaMonkey