If you’ve not been offered any security updates since January there’s a reason. It appears that some Antivirus programs make unsupported API calls to Windows kernel memory that interfere with January’s updates (especially Meltdown and Spectre patches) and may lead to BSoDs (Blue Screen of Death). To protect customers Microsoft have stopped offering security updates to devices with unsupported AVs.
While waiting for a fix from AV vendors (and if you’re absolutely sure you know what you’re doing) you can temporarily disable the compatibility check. The fix is just a registry key:
Path: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\QualityCompat Type: REG_DWORD Value: cadca5fe-87d3-4b96-b7fb-a231484277cc Data: 0x00000000
According to Microsoft as of March 13-th most of the AV vendors have fixed their products so the compatibility check will be removed soon.
You can find more information here:https://support.microsoft.com/en-us/help/4072699/windows-security-updates-and-antivirus-software