https://security.stackexchange.com/a/95070

https://en.wikipedia.org/wiki/Phishing#Spear_phishing

[deleted]

As I mentioned, the real issue is around considering of this data as a secret.

Phishing and persecution are real things that happen and can be greatly facilitated by personal details like this.

Just to clarify to the downvoters: I meant "Secret" as in password, not as in "private data". It is a private data, but it shouldn't be used as a secret to pass some security check.

Where in the article does it say that the leaked information is used as a secret to pass security checks?

You are attacking a straw man here.