There should be no drop zone for attachments while in Display mode (especially the whole page!)

Whilst a whole-page drop zone may be seen as a useful feature by some (and a major annoyance by others), it is not appropriate when the page is not being edited.

The expected behaviour for dropping a file onto a browser window is to open that file, unless there is a specifically designated drop zone. If that is the edit area of a wiki, then it is plausible for this to upload the file.

Nonetheless, while in display mode, there should be no option for unchecked or implicit uploading of attachments. In particular, users should not be able to attach files if they can't edit the page (particularly if they can't remove those attachments).

Recommended fix is to remove the drop zone altogether when in Display mode.
An option is to ask for verification in the modal lightbox before uploading the file.