It is certainly not processing under your control. You don't do anything with the data - none of your computers are involved, you never see or read or copy anyo

It is certainly not processing under your control. You don't do anything with the data - none of your computers are involved, you never see or read or copy anyone's data whatsoever. The data subject is processing their own data, using a tool they perhaps don't understand (if the source code is unavailable, for example). The user is at liberty to start or stop the processing at any time. I don't even think this would apply in the pathological case where a bug in the app causes the personal data to be leaked. You didn't leak it, the user did.