This will allow any host name again and only show a warning. This is not the wanted behavior as it will reintroduce the vulnerability.

The wanted behavior would be:
 1. Having a check at the top of `OC::handleRequest()` (https://github.com/owncloud/core/blob/master/index.php#L30) whether the domain is trusted
 2. If the domain is not trusted: Show a warning, can be the same layout as the 404 page with just another text, then the connection should be closed (e.g. exit or return)
 3. If the domain is trusted: Proceed as usual