SECURITY: Ensure oAuth authenticated email is the same as created user's email.

app/services/user_authenticator.rb

@@ -21,7 +21,10 @@ class UserAuthenticator
   end
 
   def finish
-    authenticator.after_create_account(@user, @session) if authenticator
+    if authenticator && authenticated?
+      authenticator.after_create_account(@user, @session)
+    end
+
     @session = nil
   end
 

spec/components/auth/user_authenticator_spec.rb

@@ -0,0 +1,36 @@
+require 'rails_helper'
+
+RSpec.describe UserAuthenticator do
+  let(:user) { Fabricate(:user, email: 'test@discourse.org') }
+
+  describe "#finish" do
+    before do
+      SiteSetting.enable_google_oauth2_logins = true
+    end
+
+    it "should execute provider's callback" do
+      user.update!(email: 'test@gmail.com')
+
+      authenticator = UserAuthenticator.new(user, { authentication: {
+        authenticator_name: Auth::GoogleOAuth2Authenticator.new.name,
+        email: user.email,
+        email_valid: true,
+        extra_data: { google_user_id: 1 }
+      }})
+
+      expect { authenticator.finish }.to change { GoogleUserInfo.count }.by(1)
+    end
+
+    describe "when session's email is different from user's email" do
+      it "should not execute provider's callback" do
+        authenticator = UserAuthenticator.new(user, { authentication: {
+          authenticator_name: Auth::GoogleOAuth2Authenticator.new.name,
+          email: 'test@gmail.com',
+          email_valid: true
+        }})
+
+        expect { authenticator.finish }.to_not change { GoogleUserInfo.count }
+      end
+    end
+  end
+end

spec/controllers/users_controller_spec.rb

@@ -611,6 +611,8 @@ describe UsersController do
           auth = session[:authentication] = {}
           auth[:authenticator_name] = 'twitter'
           auth[:extra_data] = twitter_auth
+          auth[:email_valid] = true
+          auth[:email] = @user.email
 
           post_user