(This is not a repeat question to "How is Facebook accessing my iPhone texts in order to recommend friends?", on StackExchange Security, linked below. I wish to know the internal details of how downloading the Facebook app on a smartphone allows Facebook to see SMS data, particularly from iMessages. I am asking for the technical details here.)
Assuming the answers to this question are correct: https://security.stackexchange.com/questions/96772/how-is-facebook-accessing-my-iphone-texts-in-order-to-recommend-friends
Is there a SDK or private framework that can access iMessage contents from an iOS app on a non-jailbroken phone?
The previous topic discussed Facebook: Is the Facebook smartphone app able to access SMS data? Somehow, downloading the Facebook app grants Facebook access to SMS data via iMessages (if you use an iPhone). I would like to understand how this works.
What other data is Facebook able to access on smartphones as soon as you download the FB app?