Eh? So why weren't they revoked entirely? I'm sure something's just unsaid there, or lost in communication or something, but as written that doesn't really make sense to me?
That is, I'd expect there was a flag in a database somewhere saying that those service accounts were "abandoned" or "cleaned up" or some other non-active status, but that this assertion was incorrect. Then they probably rotated all the passwords for active accounts, but skipped the inactive ones.
Speaking purely about PKI and certificate revocation, because that's the only similar context that I really know about, there is generally a difference between allowing certificates to expire, vs allowing them to be marked as "no longer used", vs fully revoking them: a certificate authority needs to do absolutely nothing in the first case, can choose to either do nothing or revoke in the second case, and must actively maintain and broadcast that revocation list for the third case. When someone says "hey I accidentally clobbered that private key can I please have a new cert for this new key," you generally don't add the old cert to the revocation list because why would you.
Great call out too
> Note that this was in no way an error on the part of AWS, Moveworks or Smartsheet. These were merely credentials which we failed to rotate.
i.e. instead of 'because they were mistakenly thought to be unused' you can say 'because they were mistakenly thought to be ok to leave as unused' (or something less awkward depending on exactly what the scenario was) and there's no more blame there? And if you really want to emphasise blamelessness you can say how your processes and training failed to sufficiently encourage least privilege, etc.
Because if you take it exactly as it's written it's just too weird, I'm not a security expert with something to teach Cloudflare about err maybe don't leave secrets lying around that aren't actually needed for anything, that's not news to many people, and they surely have many actual security people for whom that would not even be a fizzbuzz interview question reviewing any kind of secret storage or revocation policy/procedure. And also the mentioned third-party audit.