CentOS Errata and Security Advisory 2007:0078
https://rhn.redhat.com/errata/RHSA-2007-0078.html
The following updated files have been uploaded and are currently syncing to the mirrors:
i386: thunderbird-1.5.0.10-0.1.el4.centos.i386.rpm
src: thunderbird-1.5.0.10-0.1.el4.centos.src.rpm