Attempting to login with my MusicBrainz account gives the following error after clicking the allow access button:

Internal server error
hostname 'musicbrainz.org' doesn't match either of 'bookbrainz.org', 'test.bookbrainz.org', 'www.bookbrainz.org'

The above error also happens on trying to login to ListenBrainz and probably others. There is in fact, already a LB ticket for this same issue (LB-91).