This Motherboard article has more details on the app including screenshots https://www.vice.com/en_ca/article/y3m33x/heres-the-shadow-i...
My favorite screenshot is the last one, it looks like a generic mobile Firefox error for a misspecified URL.
My favorite screenshot is the last one, it looks like a generic mobile Firefox error for a misspecified URL.
I don't want to speculate too much on that screenshot but it looks like they have an error in their Auth0 integration. When you use a service like Auth0 you give it a redirect url to send authenticated users to. It looks like they passed in an invalid url for that redirect. Maybe they only tested this 2fa step locally and something was different when they deployed to users' phones, I can't say for sure, but it doesn't look good.
One possible issue is that Fennec/Fenix doesn't open http URLs in external apps by default (unsure about custom protocols), whereas Chrome does.