Players Dropping Icons/images into games

This has only come up a few times, and i'm not sure how it is done? I've seen players drop icons on maps that aren't in the journal, they have no GM rights, and The GM doesn't have them in library. Also seen them added to Sheets too, in the text bars. I can select and delete them but is this a hidden feature?

My understanding is player can drag and drop from the Journal any character they control and have access to. The image library should not be accessible to a player.  If you have promoted someone to GM they can access the image library. Character sheets allow them to use images for an avatar from their own library. 

Mark (GM) said: My understanding is player can drag and drop from the Journal any character they control and have access to. The image library should not be accessible to a player.  If you have promoted someone to GM they can access the image library. Character sheets allow them to use images for an avatar from their own library.  I know all that, and as i said, this is not what they are doing. They are dragging images on to the board that are not sourced from those places.

Have you asked them? They may be using a third party script or extension. They can also drag an image onto their bio, and I believe, drag the bio image onto the VTT in a two-step process. I've never tested this, though.