Check whether the blender is leaking from the lid or the base of the goblet. Also check that the filler cap is in place, and that the lid is in place correctly. If it is leaking from the top, then it is likely it has been overfilled.
If it is leaking from the bottom, make sure the base in screwed on tightly and that the rubber seal is in place. If this is missing or damaged, then the blender is not watertight. A replacement seal is needed.