Drag and drop event ckeditor

CKEDITOR.on('instanceReady', function (ev) {
   // Prevent drag-and-drop.
   ev.editor.document.on('drop', function (ev) {
      ev.data.preventDefault(true);
   });
});

var dragstart_outside = true;
ev.editor.document.on('dragstart', function (ev) {
   dragstart_outside = false;
});
ev.editor.document.on('drop', function (ev) {
   if (dragstart_outside) {
      ev.data.preventDefault(true);
   }
   dragstart_outside = true;
});

Between 'instanceReady' and 'drop', you need to add 'contentDom'...Something like this:

CKEDITOR.on('instanceCreated', function(ev) {
        ev.editor.on('contentDom', function() {
            ev.editor.document.on('drop', function(ev) {
               ev.data.preventDefault(true); 
            }
        );
    });
}); 

CKEDITOR.plugins.add('myplugin',
        {
        init: function (editor) {

            function onDragStart(event) {                 
                console.log("onDragStart");
            };

            editor.on('contentDom', function (e) {                
                editor.document.on('dragstart', onDragStart);
                // editor.document.on('drop', onDrop);
                // etc.
            });
        }
});

If this thread is still relevant, this worked in a plugin...