Wall Street Journal testing revealed that at least 11 popular apps, with millions of downloads to date, have been sharing highly personal data with Facebook.
Details: When users share their body weight, blood pressure, menstrual cycle, or pregnancy status with certain apps, that information is sent to Facebook and often matched with the Facebook profile of that user. At least 6 of the top 15 health and fitness apps in Apple’s iOS store — including iFlo Period & Ovulation Tracker and Instant Heart Rate: HR Monitor — sent sensitive user data to Facebook immediately after the information was collected. Per the WSJ, these apps frequently send this data without any disclosure to users.
Go deeper: What Facebook knows about you