The MusicBrainz OAuth2 service, like many other OAuth2 services, supports the use of urn:ietf:wg:oauth:2.0:oob to indicate that the client application can't/won't be listening on any port, but instead will need the user to input the response code (so the OAuth2 server should display it).

Please add support for this to the CritiqueBrainz OAuth2 service too.