Anything that could ever appear in an http transaction. Which is to say, anything. This is like asking what possible sensitive information a piece of paper migh

Anything that could ever appear in an http transaction. Which is to say, anything. This is like asking what possible sensitive information a piece of paper might have. If you just mean unseen info that wasn't obviously displayed right on the screen where the original user will know not to be careless with the archive of that page, the answer is still anything.