Ask HN: How to Detect Snooping in iOS Apps?

I have the official Instagram app on my phone. Today I received a text message from a friend (SMS) wherein he suggested I joined a certain organization which isn't relevant for me at all. An hour later I open Instagram and see an add for this organization.

Seeing how Im not at all their target audience, it made me suspicious. I know full well that one example does not make a case, so Im wondering if there are any tools I can use to learn more about the inner processes in Instagram?

(did check app settings, it was mostly restricted except "Background App Refresh")