Symbiosis: Publish CAA (DNS TXT) records to improve security
Certification Authority Authorization (CAA), specified in RFC 6844 in 2013, is a proposal to improve the strength of the PKI ecosystem with a new control to restrict which CAs can issue certificates for a particular domain name. It prevents bad people obtaining certificates from rogue or sloppy certification authorities.
It's a simple DNS text record to say, for example:
example.org. CAA 128 issue "letsencrypt.org"
At minimum, we could publish this record for a domain that's protected by a LetsEncrypt certificate.