CentOS Errata and Security Advisory 2008:0908
https://rhn.redhat.com/errata/RHSA-2008-0908.html
The following updated files have been uploaded and are currently syncing to the mirrors:
x86_64: thunderbird-1.5.0.12-16.el4.centos.x86_64.rpm
src: thunderbird-1.5.0.12-16.el4.centos.src.rpm