CentOS Errata and Bugfix Advisory 2015:1026 

Upstream details at : https://rhn.redhat.com/errata/RHBA-2015-1026.html

The following updated files have been uploaded and are currently 
syncing to the mirrors: ( sha256sum Filename ) 

i386:
cc26b9f3b4035b45d050b3dc7a47fc501378f345d98a7325a05aa8ced915db95  firefox-38.0.1-2.el5.centos.i386.rpm

x86_64:
cc26b9f3b4035b45d050b3dc7a47fc501378f345d98a7325a05aa8ced915db95  firefox-38.0.1-2.el5.centos.i386.rpm
077e71e9d092af8f71be5e8e8a3302462d15c4954cca0629acaf860fb3cea201  firefox-38.0.1-2.el5.centos.x86_64.rpm

Source:
f6f39fea1d96a709691c6c6b0fb8a2116765c1cc1f49e027970d973e3e00d760  firefox-38.0.1-2.el5.centos.src.rpm