User-Agent:       Mozilla/5.0 (Windows NT 6.1; WOW64; rv:44.0) Gecko/20100101
Firefox/44.0
Build Identifier: 

The recent (installed today) update to KDE/Plasma 5 completely disables the KDE
GUI; after installing the update it was not possible to log out of the GUI
without rebooting the system, and after a reboot logging in results in a black
screen with only the mouse pointer appearing.

Reproducible: Always

Steps to Reproduce:
1.Install the update.
2.Reboot
3.Login
Actual Results:  
Black screen with only the mouse pointer showing. No login sound.

Expected Results:  
Plasma 5 desktop.

Using SNAPPER to revert the file system back to its pre-update state works
around the problem, but it is necessary to use YaST to block the update
afterwards.