(This is not a repeat question to "How is Facebook accessing my iPhone texts in order to recommend friends?", 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: How is Facebook accessing my iPhone texts in order to recommend friends?
How does the Facebook app 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?