Certificate pinning (HPKP) is browsers is effectively dead, and was never a good idea to begin with. There are far too many ways to self-DoS accidentally with

Certificate pinning (HPKP) is browsers is effectively dead, and was never a good idea to begin with. There are far too many ways to self-DoS accidentally with HPKP. Also, an attacker who briefly gains control of your public DNS or web server can DoS a hostname semi-permanently.