Okay, so:
-Android: 6.0.1 (after yesterday's update)
-Basically the ones I have, Facebook and Instagram. And after the update I can't send photos on Viber and Messenger as well. I tried to upload photo here as a reply for the exact wording of the error but it did not let me to, so websites become a problem too.
-When I try to post the photo it gives me ''Allow Facebook to access photos, media, etc on your device?'', I press on allow and it gives me after that ''Screen overlay detected'' and to change this permission I have to turn off the screen overlay from Settings>Apps. So I go and turn the app overlay off and no change after that, still the same error.