A libX11 security update has been released for CentOS 7.

CESA-2021:3296 Important CentOS 7 libX11 Security Update

CentOS Errata and Security Advisory 2021:3296 Important

Upstream details at :   https://access.redhat.com/errata/RHSA-2021:3296

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

x86_64:
c053243ee1cb35d96150add59e7a1c0861276f5b2a3a9ca734501801a605c029 libX11-1.6.7-4.el7_9.i686.rpm
9d8f852847d542b8ca3a8f7afddddd363dfd43bfa65cfbf6dfc8aa04498417da libX11-1.6.7-4.el7_9.x86_64.rpm
2c6eb5afea1c0a0fa2d5103b42a1dfd64c5d9d81d7974ab2bf5adbf20f29033a libX11-common-1.6.7-4.el7_9.noarch.rpm
a11e1ecb8f7034384a2138c08abe5aa5f4f9996c624112e951eb5a42353bc197 libX11-devel-1.6.7-4.el7_9.i686.rpm
938bca67aabbf5f68ed289ef571582f9e1c3c144f27c0cc38dc3b60c03bb184e libX11-devel-1.6.7-4.el7_9.x86_64.rpm

Source:
5f8ad1a6ada2c9d49312e9f11a7c4a743d6014e87ceb75449c9e25f66eebe698 libX11-1.6.7-4.el7_9.src.rpm