Any brand you are referring to?
this is something may helps on your trouble, however if user changed the login username or password, it will totally no helps for you.
^-^ Good Luck
CANON default login
username: 7654321
password: 7654321
Fuji Xerox default login
username: 11111
password: x-admin
Konica Minolta default login
username: 12345678
password: 12345678
