attiny85 drops voltage level on an output pin... why?
You have that channel set to "AC coupling" instead of "DC coupling".  Every scope will have these settings, although there are lots of different ways they can be set.  High end scopes may have a selector knob.  Newer and lower end scopes will probably have a menu selection for that.  Look around in the choices you get associated with the "channel" that you have the scope probe plugged into.