His Pinterest bio temporarily said, "Don't worry, we are just testing your security."
By the time we published, the defacement had been removed.
But the group would not say, when asked, how it carried out the hack -- but it did say that it wasn't through leaked databases.
When pressed, the group said that it has "a exploit on Pinterest" but didn't say how. The last time it said that it had exploited a platform, it turned out to be a fake.
The group is best known for targeting high-profile users -- such as company bosses and tech executives -- and defacing their web accounts with their name and a contact address.
Their hope is that the victims reach out for security advice, which the group's website claims to provide.
The hackers also emailed me Zuckerberg's username, which is publicly known, and his password for his Twitter account, which we are not publishing for obvious reasons. The group said that the Facebook chief had enabled two-factor authentication after the first instance of the group taking over his account.
The phone number associated with the account ended in "86", according to the hackers.
The hackers also said that the current Twitter password was Zuckerberg's former personal Gmail password, which was changed six months ago.