Important Note August 29, 2023: A corrected setup is available for the Windows version of ArcGIS Server 10.9.1 Map and Feature Service Security 2023 Update 1 Patch to resolve failures with the Patch Notification tool when using the Install All Patches or Install All Security Patches options, as well as a failure when installing the patch in silent mode. If the ArcGIS Server 10.9.1 Map and Feature Service Security 2023 Update 1 Patch is already installed, there is no need to also install this new setup. The Linux setup is not affected.