Printers usually have default settings that allow firmware updates to be installed.
We advise that menu items such as Update settings are turned off
e.g.
1) On the Home Page of the printer interface, select [Setup].
2) Select [Service]
3) Select [LaserJet Update]
4) Select [Manage Updates]
5) Select [Check Automatically: Off]
6) Press the Home button to return to the main screen.
7) Repeat Steps 1-4, and on the Manage Updates screen select [Allow Updates: No]
8) Repeat Steps 1-4, and on the Manage Updates screen select [Allow Downgrade: Yes]
9) Press the Home button to return to the main screen.