Microsoft has released Security Updates (SUs) for vulnerabilities found in:
Exchange Server 2013
Exchange Server 2016
Exchange Server 2019
SUs are available in a self-extracting auto-elev...
Updated May 08, 2023
Version 22.0
Blog Post
Nino_Bilic The_Exchange_Team we are still facing issues with add-ins after installing the March SU. We are 100% Exchange 2016, no 2013. Symptoms are that some users, but not all, notice their add-ins disappear, and are not able to load the Manage Add-ins page in OWA. If we do "Get-App -mailbox <user>" on the affected user mailbox it fails.
The workaround mentioned by others in this thread and the Feb SU thread DOES work for us (i.e. Set-App -organizationapp -identity <appid> -userlist <user>), but as we rolled through our patching process with all of our Exchange servers over the past few days we had to run this workaround at least three times. Each time was either the built-in My Templates or Action Items add-in that we had to do the Set-App on.
Is Microsoft aware of this issue? Is it the same issue that you list under the "resolved issues"?