Every .dk domain that delegates its _acme-challenge name to c38baf35-2fc5-4d40-bd89-1d61e6f54dc3.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.