Ask HN: What actual Facebook data fields were obtained by Aleksandr Kogan?

I know that when a user provides permission, a Facebook third-party app can obtain certain information from Facebook about the user. From what I understand, Aleksandr Kogan obtained some information about users' friends. My question is, what information was originally permitted to be seen by the third-party app. I thought in most cases, it was just the name/id of the friend. Obviously, if a user's friend is public, much more can be obtained but does anyone know what data fields were actually obtained by Aleksandr?