A firefox security update has been released for CentOS 7.

CESA-2021:2741 Important CentOS 7 firefox Security Update

CentOS Errata and Security Advisory 2021:2741 Important

Upstream details at :   https://access.redhat.com/errata/RHSA-2021:2741

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

x86_64:
d09bdd004c3fac87661119d619afb43d9ad9824ef8a2e58fa51c55f0211f12d9 firefox-78.12.0-1.el7.centos.i686.rpm
6a6db0a030199ad5a8e0edde0f8458ca5391f94ac4ccd7a93c3c186326026cc3 firefox-78.12.0-1.el7.centos.x86_64.rpm

Source:
fd28ed7ab0523d22a76adadf6f4da17f29f7bba08cc83e43af80bf3e0bd490b0 firefox-78.12.0-1.el7.centos.src.rpm