Every .dk domain that delegates its _acme-challenge name to 72911c48-3cdc-4cba-8ec9-d6def2b87eb1.auth.acme-challenge.dk. Such CNAMEs hand DNS-01 certificate validation to a shared service, so this list shows who issues TLS certificates through it. Data comes from our own scanners, which re-resolve every .dk domain in the zone roughly once a week.