Certificate flooding attack points out weaknesses in the OpenPGP infrastructure. Certificate flooding attacks have been known for years, but this attack appears to be unprecedented. The attack was never addressed because of a variety of barriers, including the fact that the keyserver system generally worked. The attacks illustrate the fragility and necessity of projects such as PGP, a cryptographer and cryptographer says. One analyst said that while PGP and tools that depend on it have value still, they shouldn’t be best option for people in high-risk situations.”]
Source: https://duo.com/decipher/openpgp-certificate-attack-worries-experts