Mozilla has released Firefox 3.6.13 & Thunderbird 3.1.7. Download them from the previous links or update from within the program (Help / Check for Updates).
Firefox 3.6.13 fixes the following issues found in previous versions of Firefox 3.6:
* Fixed several security issues.
* Fixed several stability issues.Thunderbird 3.1.7 fixes the following issues in Thunderbird 3.1.6:
* Several fixes to improve performance, stability and security, see the Security Advisory.
* Several fixes to improve handling of large folder files stored locally.
* Several fixes to improve corruption in local copy of IMAP mailboxes.