Several weeks ago, I developed my own service that uses Google's oauth2 for authentication. It used a popup window method to reach Google's oauth2. It worked for both Chrome and Firefox. Then, I noticed that oauth2 UI has changed a bit and the popup on Firefox is no longer work, yet it still works on Chrome. This happened exactly on 17 Dec 2018. I fixed that by changing the method to reloading the callback in the same tab/window without popup and it's fine on both Chrome and Firefox. Since then, I found more services that use the popup method against Google oauth2 were no longer work on Firefox. Some of them fixed it by moving to reload method.
I'm not sure whether the Firefox update or Google's oauth2 update that has caused this.
Is there anyone experienced this? If your service uses the oauth2 + popup method, you may check if it still works on Firefox.