Millions of smartphone users confess their most intimate secrets to apps, including when they want to work on their belly fat or the price of the house they checked out last weekend. Other apps know users’ body weight, blood pressure, menstrual cycles or pregnancy status.

Unbeknown to most people, in many cases that data is being shared with someone else: Facebook Inc.

The social-media giant collects intensely personal information from many popular smartphone apps just seconds after users enter it, even if the user has no connection to Facebook, according to testing done by The Wall Street Journal. The apps often send the data without any prominent or specific disclosure, the testing showed.

It is already known that many smartphone apps send information to Facebook about when users open them, and sometimes what they do inside. Previously unreported is how at least 11 popular apps, totaling tens of millions of downloads, have also been sharing sensitive data entered by users. The findings alarmed some privacy experts who reviewed the Journal’s testing.

Facebook is under scrutiny from Washington and European regulators for how it treats the information of users and nonusers alike. It has been fined for allowing now defunct political-data firm Cambridge Analytica illicit access to users’ data and has drawn criticism for giving companies special access to user records well after it said it had walled off that information.