Exchange 2019 CU12/13 Security Update 13 is expected to enable PowerShell serialization by default. This feature configures certificate-based signing of PowerShell serialization payloads to reduce the possibility of man-in-the-middle attacks in PowerShell scripts that connect to Exchange server.
PowerShell serialization requires prerequisites, which the link above describes:
It's unlikely that the SU installer will check for these prerequisites, so this may cause problems with Exchange scripts in your environment if the prerequisites are not met but the SU enables PowerShell serialization.
The best course of action is to check the prerequisites first, especially if you don't read the SU installation notes first or you use Windows Update to deploy this security update.