A thunderbird security update has been released for CentOS 7.

CESA-2021:3841 Important CentOS 7 thunderbird Security Update

CentOS Errata and Security Advisory 2021:3841 Important

Upstream details at :   https://access.redhat.com/errata/RHSA-2021:3841

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

x86_64:
69ae41a6c3ac23339ec68078341f79bf409340725c4349483ba59ace78f79028 thunderbird-91.2.0-1.el7.centos.x86_64.rpm

Source:
2c5ef7f7281f2aa16ad9c0c8179703f8980c388e43bb0add565e73005addb358 thunderbird-91.2.0-1.el7.centos.src.rpm