A thunderbird security update has been released for CentOS 7.

CESA-2021:4134 Important CentOS 7 thunderbird Security Update

CentOS Errata and Security Advisory 2021:4134 Important

Upstream details at :   https://access.redhat.com/errata/RHSA-2021:4134

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

x86_64:
36259b436231dc4bfc0fb0c9db4b4bcb6693260e26b5c858fed3e11c71a5be0a thunderbird-91.3.0-2.el7.centos.x86_64.rpm

Source:
38c680ecadd599b7195652d34ac032c350a2b98be21334d5891f248862e840fc thunderbird-91.3.0-2.el7.centos.src.rpm