It can be else, but can't really think of an occasional large leak not being caused by something like that. Call it fluke...or badly formulated modern detergent.
If you have bad pump pipe's seals or faulty seals of the round pump block or element.. the thing would likely leak every time you put water in it, sure enhanced by hot water but it'd happen always....
The detergent cup could also give occasional leaks similar to it, but we're talking of a compromised situation and a leak that already goes on from awhile but minimal, depending on how you load it, water may be sprayed on the cup with more or less force....in the first case, the leak will be more evident than a little stream that until then stayed within the door panel even though it likely goes on from awhile before, this may be a dried/faulty seal of the cup.
Detaching the front panel will immediately give you a picture if that's the case, if you'll see white/residues water marks or water "streams" coming from the cup housing then that's the problem, easy replace really once you got the right part...pop out the cup, put in the new seals some cleaning of cup's solenoid contacts and area with WD40, Pb Blaster etc and it'll be fine.
Easy job really....