The OS could provide a dedicated button of its own for pasting images, etc. It could be recognizable and standard and apps could embed it as needed. The key is

The OS could provide a dedicated button of its own for pasting images, etc. It could be recognizable and standard and apps could embed it as needed. The key is that apps shouldn't have silent, arbitrary clipboard access. The user should have to do an action for the clipboard's contents to be transferred. The only way to prevent abuse is for a system-provided widget to be the one making the actual API call. Another option would be to provide apps an API call that opens a system "paste dialog", asking the user, "Paste X into this app?". This would have the added bonus of giving the user a preview of what they have in their clipboard before actually performing the paste. It could even show a history of the last several copied items in case they want to paste one of those instead, which would be a genuine productivity-booster.