Microsoft has confirmed the issue.
https://learn.microsoft.com/en-us/windows/release-health/status-windows-11-22H2#3048msgdesc
After installing "Update for Microsoft Defender Antivirus antimalware platform - KB5007651 (Version 1.0.2302.21002)", you might receive a security notification or warning stating that "Local Security protection is off. Your device may be vulnerable." and once protections are enabled, your Windows device might persistently prompt that a restart is required. Important: This issue affects only "Update for Microsoft Defender Antivirus antimalware platform - KB5007651 (Version 1.0.2302.21002)". All other Windows updates released on March 14, 2023 for affected platforms (KB5023706 and KB5023698), do not cause this issue.
Workaround: If you have enabled Local Security Authority (LSA) protection and have restarted your device at least once, you can dismiss warning notifications and ignore any additional notifications prompting for a restart. You can verify that LSA protection is enabled by looking in Event Viewer using the information available here. Important: Currently, we do not recommend any other workaround for this issue.
Next steps: We are working on a resolution and will provide an update as soon as it is available.