For a new web developer or firse-time firebase user going through the firebaseui-web tutorial sequentially in github, they will experience an issue if they try to support login through one of our federated providers and test it locally in the file environment.

This can be easily resolved if the user uses the Firebase CLI, using firebase serve so it goes through localhost, but an introduction to this is missing in the Github. Perhaps we could also make the error code message indicate this solution so developers will know where to go.