From MFSA 2008-43: Microsoft developer Dave Reed reported that certain BOM characters are stripped from JavaScript code before it is executed. This can lead to code, which would otherwise be treated as part of a quoted string, to be executed. The issue could potentially be used by an attacker to bypass or evade script filters and perform an XSS attack.
This is now public
thunderbird-2.0.0.18-1.fc8 has been pushed to the Fedora 8 stable repository. If problems still persist, please make note of it in this bug report.
thunderbird-2.0.0.18-1.fc9 has been pushed to the Fedora 9 stable repository. If problems still persist, please make note of it in this bug report.
This was addressed via: Red Hat Enterprise Linux version 4 (firefox) RHSA-2008:0879 Red Hat Enterprise Linux version 5 (firefox) RHSA-2008:0879 Red Hat Enterprise Linux version 2.1 (seamonkey) RHSA-2008:0882 Red Hat Enterprise Linux version 3 (seamonkey) RHSA-2008:0882 Red Hat Enterprise Linux version 4 (RHSA-2008:0882) Red Hat Enterprise Linux version 4 (thunderbird) RHSA-2008:0908 Red Hat Enterprise Linux Desktop version 5 (thunderbird) RHSA-2008:0908 RHEL Optional Productivity Applications version 5 (thunderbird) RHSA-2008:0908