A thunderbird security update has been released for CentOS 7.

CentOS-announce: CESA-2020:3344 Important CentOS 7 thunderbird Security Update

CentOS Errata and Security Advisory 2020:3344 Important

Upstream details at :   https://access.redhat.com/errata/RHSA-2020:3344

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

x86_64:
1843f66766dd4e3ec0481895eb214582b167995238898e2666b1dcb523e0a7a1 thunderbird-68.11.0-1.el7.centos.x86_64.rpm

Source:
ad6d42bca1ff78685b464bb05fab28a9ddedde5fc9c7a4a71de77fef45fedc6d thunderbird-68.11.0-1.el7.centos.src.rpm