The Facebook internal team discovered a photo API bug that may have affected people who used Facebook Login and granted permission to third-party apps to access their photos. We have fixed the issue but, because of this bug, some third-party apps may have had access to a broader set of photos than usual for 12 days between September 13 to September 25, 2018.
Affected Facebooks Users?
Currently, we believe this may have affected up to 6.8 million users and up to 1,500 apps built by 876 developers. The only apps affected by this bug were ones that Facebook approved to access the photos API and that individuals had authorized to access their photos.
Reference of full stories by the facebook team