Popular mobile apps send sensitive personal data to Facebook by using Facebook's SDK to collect this data:
https://www.cnet.com/news/facebook-receives-personal-info-like-your-heart-rate-from-popular-apps/
– at least 11 out of 70 popular apps are affected
– sensitive data includes blood pressure, pregnancy status, menstrual cycles, heartbeat rates, viewed real estate postings etc.
– some of these apps are "Instant Heart Rate", "Flo Period & Ovulation Tracker", "Realtor.com"
– also affects users without Facebook accounts