Every .dk domain that delegates its _acme-challenge name to c2b4bf8b-7f19-4f1d-bcb3-a28bc8dea20f.18.authorize.certificatemanager.goog. 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.