Google OAuth Login Android "Access blocked" error 403 access_denied to some users

Question

I've integrated Google SIgn-In library into my Android APP (which is already in production) and 95% of the users can login without any problem, however, there is a small number of users who reports that when they try to login within the APP, this error message prompts in:

Where is this verification process located? Since the only fields I request is the email of the users, I didn't completed any kind of form. It is necessary?

 GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken(WEB_CLIENT_ID)
                .build();

I'm really confused since as I said, 95% of the users can login without problems and I've tried to contact Google but they simply ignored my message. Any hint?

Answer 1

This is probably caused by Google Security Attestation mechanism，Google sign-in lib may check the environment of user's device,if the device is rooted or debuggable or in developing mode,the lib shall block the access.So suggest you to check the Google sign-in api doc to find if there is any permission description,meanwhile you can try to confirm if their(users who have sign-in issues) devices are in one of those situations I mentioned above.