What happens to images that are uploaded, but never used?

I recently discovered that you can paste image data from your clipboard to a post or comment field, and it will upload the data and generate an embed link. I assume, since the clipboard is ephemeral, that the data is uploaded and stored on the server immediately.

What happens then if the embed link is removed and never used, but the file isn't deleted by the user? Does it just sit around in storage, collecting dust and taking up space, or is there some sort of garbage collection that detects unused files? What happens to embedded files if the post/comment where it is embedded gets deleted?