I'm having issues adding a CORS setting for

<http://127.0.0.1:80>

I am able to add http://localhost:8080 Any idea what sort of client side validation is failing?

try adding

<http://localho.st>

and access your app via http://localho.st/ (assuming your app is really running on port 80 of 127.0.0.1, then it should work). I think the validation is too restrictive and doesn't allow entering IP addresses via UI.