0 July 2021 Updates for Exchange Released Less than two weeks after the release of the cumulative updates for Exchange 2016 and Exchange 2019, we now have a critical security update for all supported versions of Exchange (so 2013 and up).Fortunately Microsoft have released updates for both the current and previous cumulative update for Exchange 2016 and Exchange 2019, but for Exchange 2013 they are are only released for CU23.Full details: https://techcommunity.microsoft.com/t5/exchange-team-blog/released-july-2021-exchange-server-security-updates/ba-p/2523421However this update requires something new - after installing the update on EXCHANGE 2013 or anything but the latest CU for Exchange 2016 and Exchange 2019, you have to run a schema update. That is something new, but is required because of the issue that has been fixed. The blog posting I have linked to above has full details.Therefore the decision is whether to deploy the cumulative update and then the the security update, or wait a bit longer on the CU. That may mean that the security update has to be applied twice if you wait.What I would suggest is that you deploy the CU, reboot and then deploy the security update - in the same downtime window.
