Starting with November 2023 SU, we are enabling certificate signing of PowerShell serialization payload by default (as a reminder, this is a feature that we released in January 2023 as an optional feature at the time).

Certificate signing of PowerShell serialization payload is now enabled by default More details about specific CVEs can be found in the Security Update Guide (filter on Exchange Server under Product Family). Exchange Online customers are already protected from the vulnerabilities addressed by these SUs and do not need to take any action other than updating any Exchange servers or Exchange Management tools workstations in their environment. These vulnerabilities affect Exchange Server. Although we are not aware of any active exploits in the wild, our recommendation is to immediately install these updates to protect your environment. The November 2023 SUs address vulnerabilities responsibly reported to Microsoft by security partners and found through Microsoft’s internal processes. SUs are available for the following specific versions of Exchange Server: Microsoft has released Security Updates (SUs) for vulnerabilities found in:

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