1. The Login Process When a user logs in via Facebook, Firebase retrieves their Facebook profile information. This allows a user account to be created in Firebase.
2. Facebook Limitations If the user has not verified their email address on Facebook or if permissions are limited, Firebase may create an account without associating the email address, or with a different address (e.g., [email protected] ).
3. Impact on Account Merging This may prevent automatic account merging if the user later logs in using a different method (e.g., email/password).