A thunderbird security update has been released for CentOS 7.

CESA-2021:3494 Important CentOS 7 thunderbird Security Update

CentOS Errata and Security Advisory 2021:3494 Important

Upstream details at :   https://access.redhat.com/errata/RHSA-2021:3494

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

x86_64:
6576a71997c6b88e455bd9405164a03375ea03ef6dfbfc8c070d29e8de1f5324 thunderbird-78.14.0-1.el7.centos.x86_64.rpm

Source:
a665cfdccc33a1c6f201f2415c355de3304c5d27dadafae35c6024b1aef78d3d thunderbird-78.14.0-1.el7.centos.src.rpm