The following errata for CentOS-2 have been built and uploaded to the centos mirror:

RHSA-2006:0676-01 Critical: seamonkey security update

Files available:
seamonkey-1.0.5-0.0.1.el2.c2.1.i386.rpm
seamonkey-chat-1.0.5-0.0.1.el2.c2.1.i386.rpm
seamonkey-devel-1.0.5-0.0.1.el2.c2.1.i386.rpm
seamonkey-dom-inspector-1.0.5-0.0.1.el2.c2.1.i386.rpm
seamonkey-js-debugger-1.0.5-0.0.1.el2.c2.1.i386.rpm
seamonkey-mail-1.0.5-0.0.1.el2.c2.1.i386.rpm
seamonkey-nspr-1.0.5-0.0.1.el2.c2.1.i386.rpm
seamonkey-nspr-devel-1.0.5-0.0.1.el2.c2.1.i386.rpm
seamonkey-nss-1.0.5-0.0.1.el2.c2.1.i386.rpm
seamonkey-nss-devel-1.0.5-0.0.1.el2.c2.1.i386.rpm

More details are available from the RedHat web site at
https://rhn.redhat.com/errata/rh21as-errata.html

The easy way to make sure you are up to date with all the latest patches is to run:
# yum update