So...Golden SAML isn't a vulnerability, as the CyberArk article quoted in the post reiterates, it's a type of attack that requires completely comprising the box before using. Unless I am misunderstanding something, I don't see any particular flaw, per se. As Microsoft (mocked in the article) would say, it's not crossing a security boundary. SSO will ALWAYS have this particular tradeoff. If your SSO infrastructure is compromised, everything that uses it is at risk of being compromised.