Device: iPad 4th gen
Os: iOS 9.2.1
So this may not necessarily be a bug as such, but the "unlock" button in the purchasing menu has yellow text over a white background, which is not exactly aesthetically pleasing from a design standpoint. Doesn't interfere with actually buying the item, but noting it anyway.
https://www.dropbox.com/s/oad2nkbfwwd18k7/2016-04-01%2015.33.18.png?dl=0