Are all images pasted from the clipboard stored, or only the ones posted?

Say a user pastes an image into a post. Is that image store on the server, since I do see an “Uploading” progress indicator?

What if the user realizes during the preview that the image had included sensitive data, so they delete the <img> markup and paste a new one? Is the old image still available on the server?

Any images or files (attachments) not referenced by a live post are periodically removed. @zogstrip wrote that code.