A thunderbird security update has been released for CentOS 7.

CentOS-announce: CESA-2020:2050 Critical CentOS 7 thunderbird Security Update

CentOS Errata and Security Advisory 2020:2050 Critical

Upstream details at :   https://access.redhat.com/errata/RHSA-2020:2050

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

x86_64:
4842f4f19ce041fd6dc1035468374c7407eb0089e84c3ce59bbb619e213db688 thunderbird-68.8.0-1.el7.centos.x86_64.rpm

Source:
351965c3a3afae1c7a85071d308933a2c1283733f174cfc8db2ce9d3cc4ba2b4 thunderbird-68.8.0-1.el7.centos.src.rpm