A thunderbird security update has been released for CentOS 7.

CentOS-announce: CESA-2020:2615 Important CentOS 7 thunderbird Security Update

CentOS Errata and Security Advisory 2020:2615 Important

Upstream details at : https://access.redhat.com/errata/RHSA-2020:2615

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

x86_64:
ab6911fa3852547565729fdebb90a6dfd7037df9b68c6c7673107494aa4acb30 thunderbird-68.9.0-1.el7.centos.x86_64.rpm

Source:
5234ba5004b097341a81536325039081e0ae1bd9310c184c6d0b634dbdff33a4 thunderbird-68.9.0-1.el7.centos.src.rpm