I added http://www.cdbaby.com/example to http://test.musicbrainz.org/release/d9207330-8a89-302a-9d7b-05b85015b896

Now both http://test.musicbrainz.org/url/0f357678-8fad-4e4d-9db8-63b3d9022236 and the edit page http://test.musicbrainz.org/url/0f357678-8fad-4e4d-9db8-63b3d9022236/edit display http://www.cdbaby.com/example/from/musicbrainz as the URL, which is wrong, as that's not the URL in the database.

If I then remove the /from/musicbrainz bit and submit the page, it even submits an edit to remove the /from/musicbrainz part which was never in the database to begin with - http://test.musicbrainz.org/edit/14460130