These Period Tracking Apps Share Your Data With Facebook or other third-party services. UK-based advocacy group Privacy International revealed how some most popular period tracker apps used by millions of women share their most private health information. The apps share user-entered data with Facebook via its software development kit (SDK) integrated into the app to help app developers earn revenue by collecting user data so Facebook can show them targeted advertisements. Facebook said it would “investigate whether the advertising platform collects users’ private data or not”
Source: https://thehackernews.com/2019/09/facebook-period-tracker-privacy.html