This feature would allow a user to configure a CNAME on a repository. The CNAME would treat the repository as if it were a static hosted repository, which we support. This would allow a user to host content on Bitbucket, directly from their repository.
This should not allow a user to direct a CNAME to a repository's landing page, nor account (ie. no Bitbucket login/UI). This could open the user to security issues, as noted in comments regarding the EOL for the current account level CNAME feature.