I was playing around a bit with Fiddler to capture traffic from the Stack Exchange iOS app. To my surprise, it uses version 2.3 of the Stack Exchange API:
I noticed here that it has some extra functions compared to the current release (v2.2), and that it wasn't documented yet. However, that answer is one-and-a-half year old; any updates on this topic? Or will this keep on being an unofficial release, only released to support some additional features for the mobile app, which as we know isn't actively developed anymore?