When trying to access the Data Explorer with my openid profile (the same one I use for all SE sites) I get a ASP.NET error page:
Server Error in '/' Application. Runtime Error Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.
But it still seems to log me in on the home page, but when I try to access any particular query I get the same error screen. If I log out I can again view the queries.
Additionally when I try to execute a query anonymously I get:
Cannot open database "StackExchange.Rpg.Exported" requested by the login. The login failed. Login failed for user 'readonly'.
Edit: Upgrading to bug because it's definitely not just a transitive issue at this point.