A recent study by Privacy International found that at least 20 Android apps with install bases in excess of 10 million users automatically send user data to Facebook within one second of opening. This data is sent without user knowledge or user consent and ranges from innocuous to personal. This practice obviously raises some questions of legality, although it is difficult to say who is to blame for the violation of user privacy and laws such as GDPR.
https://www.notebookcheck.net/At-least-20-popular-Android-apps-are-still-sending-user-data-to-Facebook-without-consent-study-finds.388211.0.html