All I have so far, is a pseudo-antonym of what I actually want: Obscurantist. The word I need should be a person who was unwillingly plagued with sensitive information. It is more of a - I don't how to describe it - pitiful connotation. (To me, "infobearer" should work, allowing for the fact that such a word does not exist...)
For example, take Bob, who accidentally got himself exposed to top secret information of some organization. And now people are after him. He is a _____?
I need a single-word noun, not an adjective.
Edit: would secret-keeper or secret-holder do the trick?