A thunderbird security update has been released for CentOS 7.

CentOS-announce: CESA-2020:3631 Important CentOS 7 thunderbird Security Update

CentOS Errata and Security Advisory 2020:3631 Important

Upstream details at :   https://access.redhat.com/errata/RHSA-2020:3631

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

x86_64:
eee32b147df145f7043c9e9f6bff219b5b7baee07773c613dda73a937fecb1ec thunderbird-68.12.0-1.el7.centos.x86_64.rpm

Source:
47a72b65f6b7fd85d69531a9fa992423075b3d355f2557dad453df8e506b9b1d thunderbird-68.12.0-1.el7.centos.src.rpm