Antivirus solutions from different vendors are showing malfunctions after the installation of Windows security patches released on April 9. Users of the affected machines are observing sudden system freezes and performance degradation. Microsoft is aware of the problems reported by its users with their antivirus solutions and already included several antivirus software to the list of known issues. The root cause of the problem is the change that Microsoft made to CSRSS (client/server runtime subsystem) component that manages Win32 applications.”]
Source: https://securityaffairs.co/wordpress/84249/breaking-news/antivirus-problems-windows-updates.html