An expat security update has been released for CentOS 7.

CESA-2022:1069 Important CentOS 7 expat Security Update

CentOS Errata and Security Advisory 2022:1069 Important

Upstream details at :   https://access.redhat.com/errata/RHSA-2022:1069

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

x86_64:
c653aaa3759f6c65e6ccf1dafa36096bf4821f315dbf756943730947258100ef expat-2.1.0-14.el7_9.i686.rpm
b0179562abc1ff5d40c03661749ce4f7f4c7d58c428cecfc4a3711bfa98e6ec6 expat-2.1.0-14.el7_9.x86_64.rpm
f4c0956c54c55adea5769904bb460f6ab64b017d31e9a73f0a047345be6dd6af expat-devel-2.1.0-14.el7_9.i686.rpm
301d479dffc9084746269cad6d9be379a3c01fafa139c9203aa5c98ca7e9d79e expat-devel-2.1.0-14.el7_9.x86_64.rpm
a962654ff0fe134fdd88392c47a711e94bc84e08e27d0a7cb7d28e9150d2999a expat-static-2.1.0-14.el7_9.i686.rpm
46c46ba8573d8f101c53fe10179a66e853ec151d66f5dfb686fb60c5e75aa610 expat-static-2.1.0-14.el7_9.x86_64.rpm

Source:
6c86a22138aaddd33328f353b445995e9a67f824e4cb25423b1e07b325142366 expat-2.1.0-14.el7_9.src.rpm