My mob farm is plagued with explosions without any players near the creepers. it's impossible for the mobs to even pathfind to the player. and the explosions happen most often in the main body of the farm 24+ blocks away from the player. in the water stream. I suspect the creepers are taking fall damage and are blaming any nearby mob for it, thus targeting them and exploding. If this is a feature and not a bug, this behaviour should be added to the wiki.

as a side note, lack of spectator mode is severely hampering me in finding if this effect is true.