This is 100% the fault of June and not the user:

June CEO Matt Van Horn says that owners, not the oven, are at fault. “We’ve seen a few cases where customers have accidentally activated their oven preheat via a device, figure your cell phone,” he tells The Verge. “So imagine if I were to be in the June app clicking recipes and I accidentally tapped something that preheated my oven, we’ve seen a few cases of that."

Carman, A. (2019, August 14). Smart ovens have been turning on overnight and preheating to 400 degrees.