That makes sense, but it raised a question on my mind: What about malicious sites? Could this be used to do something without the user knowing? One could mark

That makes sense, but it raised a question on my mind: What about malicious sites? Could this be used to do something without the user knowing? One could mark a link as prefetch and that URL would be downloaded without prompting the user. Does that impose a genuine threat, or is that something that malicious sites can already do?