HP Elitedesk 800 G4 WDF_VIOLATION error

HP EliteDesk 800 G4 systems may experience a BSOD upon startup after the installation of Windows 10 October 2018 updates.

Update 12 October:
Microsoft fix posted, KB 4468304.

If you are seeing a BSOD, please go to “Scenario 2”:

Original article:

To resolve this issue, in Windows 10 Startup Repair, enter a command prompt, go to \windows\system32\drivers , and delete hpqkbfiltr.sys .

Reboot and the system should roll back the latest updated attempted. You will then need to run Windows Updates again to re-apply the latest updates, which should install successfully.