I know this is older but just in case some one experienced the same thing, the above mentioned is true. I experienced this on iTunes on my PC quite a while ago

I know this is older but just in case some one experienced the same thing, the above mentioned is true. I experienced this on iTunes on my PC quite a while ago. And since then I have not made any purchases from the iOS device itself. I buy through the PC and then sync to my devices because of slow internet. So now, basically when I tried to make an IAP, I got the same popup. I first thought it was the app that wanted to know my details but it really is Apple. I got this out of the way by purchasing a small, 99ct app directly from my Device. So I went into the AppStore, bought the app and the same popup came up. Since this was now in the official Apple Appstore app, I answered two of my questions, downloaded the app and now, this popup is gone and I can make IAP all I like.