Every .dk domain that delegates its _acme-challenge name to 537cc0c4-0e1b-4f61-9d5a-d0a0c16e9155.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.