Microsoft is rolling out new cumulative updates to Windows 10 versions with security fixes and improvements. Microsoft has also released the May 2019 patches to users with Windows 7 and Windows 8.1 devices. The new monthly rollups come with important security fixes. Microsoft is aware of the following problems with this update: It may cause the system to have slow startup or become unresponsive at restart after installing this update. It may also cause Error 1309 while installing or uninstalling certain types of.msi and.msp files on a virtual drive.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-releases-windows-7-and-81-cumulative-updates-kb4499164-and-kb4499151/