A thunderbird security update has been released for CentOS 7.

CESA-2021:0087 Critical CentOS 7 thunderbird Security Update

CentOS Errata and Security Advisory 2021:0087 Critical

Upstream details at :   https://access.redhat.com/errata/RHSA-2021:0087

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

x86_64:
9d6dba1f2b69d9a60186e25386f8b45c69cd3fc28e58774151905a0edfac5a82 thunderbird-78.6.1-1.el7.centos.x86_64.rpm

Source:
5f6afd3684dd44a2cd4275e55a7ff11dafa7526fe9220f428582e8a35fc0aa6a thunderbird-78.6.1-1.el7.centos.src.rpm