And Vita Rays. Lots of people were in on it, and it's not like Cap wasn't a big public figure. Plus the military also got hold of it (General Ross' stash) so it can't have been that well-kept of a secret. And the entire world is trying to replicate it constantly, which is what gives Agents of SHIELD all the trouble they're usually dealing with. So I'd say maybe not general knowledge, but available if you do your research. Plus there's the Captain America exhibit in the Winter Soldier, there could feasibly be some info or a blurb about it in there.