Perhaps you are lucky enough to have never encountered this bug 
but regardless, in the video below I demonstrate the key press flow that triggers the two operations, upload and move, using KeyCastOW, so that you and others can clearly understand the specific process.
Upload - Press the left mouse button and drag directly
Move - Press the left mouse button to click and then drag
By the way, I just tested using your cat () and your other image (), and found that neither of them could trigger this issue.
I suggest you use  for testing; at least it is known to me as a test material that can reliably reproduce the issue. If you cannot reproduce the issue using it, perhaps you are just that lucky. 