Prevent Firebase auth from remembering Google account?

Question

So I'm using Firebase-UI to authenticate and sign in users, I need to use the account chooser in order for them to sign in to a different Google account (not using the account chooser results in it auto-signing them in), however, I want to either prevent it from displaying + saving accounts, or remove them on sign out.

And this is the Firebase-UI web I'm using: Firebase UI web

This isn't a huge issue when the application is running on a user's machine, however, it will also be running on a public machine with many users signing in an out, and we can't have them saved as an easy one-click sign in. The biggest security issue is the fact that I can also log into their emails once they've authenticated with Google. We want it to forget them once they sign out.

My sign-in flow:

     <script type="text/javascript">
            // FirebaseUI config.
            var uiConfig = {
                callbacks: {
                    signInSuccess: function (user, credential, redirectUrl) {
                        var userSignIn = {
                            displayName: user.displayName,
                            email: user.email,
                            emailVerified: user.emailVerified,
                            photoURL: user.photoURL,
                            uid: user.uid,
                            phoneNumber: user.phoneNumber
                        };
                        /* POST signed in user to Login Controller*/
                        var csrfToken = $('input[name="csrfToken"]').attr('value');
                        $.ajaxSetup({
                            beforeSend: function(xhr) {
                                xhr.setRequestHeader('Csrf-Token', csrfToken);
                            }
                        });
                        $.ajax({
                           url: '/signedIn',
                           type: 'POST',
                           data: JSON.stringify(userSignIn),
                           contentType: 'application/json',
                           error: function(err) {
                               console.log(err);
                           }
                        });
                        return true;
                    }
                },
                signInSuccessUrl: '/Dashboard',
                signInOptions: [{
                    provider: firebase.auth.GoogleAuthProvider.PROVIDER_ID,
                    scopes: ['https://www.googleapis.com/auth/calendar']
                }],
                // Terms of service url.
                tosUrl: '/Terms'
            };

            // Initialize the FirebaseUI Widget using FirestoreDB.
            var ui = new firebaseui.auth.AuthUI(firebase.auth());
            // The start method will wait until the DOM is loaded.
            ui.start('#firebaseui-auth-container', uiConfig);
    </script>

Sign-out flow:

initApp = function () {
firebase.auth().onAuthStateChanged(function (user) {
    if (user) {
        // User is signed in.
        if (window.location.pathname === "/Login" || window.location.pathname === "/") {
            window.location.href = '/Dashboard';
        }
        $('#sign-out').show();
    } else {
        // User is signed out.
        $('#sign-out').hide();
        disableLinks();
        switch(window.location.pathname){
            case "/Login":
            case "/Terms":
            case "/Help":
                break;
            default:
                window.location.href = '/Login';
        }
    }
}, function (error) {
    console.log(error);
});
};

window.addEventListener('load', function () {
initApp();
document.getElementById('sign-out').addEventListener('click', function () {
    firebase.auth().signOut().then(function() {
        sessionStorage.clear();
        localStorage.clear();
        window.location = "/Logout";
    }).catch(function(error) {
        console.log(error);
        });
    });
  });

Answer 1

On sign out from Firebase Auth, redirect to Google single sign out URL:

firebase.auth().signOut()
  .then(function() {
    window.location.assign('https://accounts.google.com/Logout');
  })
  .catch(function(error) {
    console.log(error);
  });