UPDATE 2019/11/14: Facebook released version 247.0 that fixes the glitch.
Joshua Maddux published on his Twitter account a video captured from an iPhone running iOS 13.2.2: in this video, a glitch in the interface of Facebook App reveals that the camera is up and running without any notification.
The bug is really simple to reproduce: simply open a Facebook page, tap on profile image and swipe down in order to close the full screen image.
After this sequence, the interface of the app fails to re-align and shows on the background the video stream captured by the rear camera.
Below the test performed on my device (iPhone 7):
I did the same test on an iPhone XS, without being able to reproduce the bug.
Now, the main question is: why the camera is on?
Is it just a stupid bug or just one of several techniques used by Facebook in order to collect data?
Relax, regardless of whether this is a bug or a data-collection feature, the remediation is pretty simple.
Without coming to buy a smartphone with camera kill-switch , or a more affordable camera cover , you can disable camera access for the facebook app, as shown by Marco De Sanctis on the twitter thread above:
For additional privacy, Marco disables also microphone and bluetooth access, that can be used by facebook for location tracking .