Jack Dorsey, Twitter CEO’s account was hacked on Friday afternoon by hackers. It was a group that calls itself the Chuckle Squad that posted rogue tweets on race, antisemitic messages and one on Holocaust denial. Some of the tweets were up for 10 minutes before it was taken down and deleted permanently.

After an hour and a half later, Twitter tweeted that

Instead, it was found that it was Dorsey’s phone number associated with the account that was compromised due to security oversight by the mobile provider.

The tweets were sent via a service Twitter bought in 2010, Cloudhopper, to improve its SMS service. It is anticipated that Dorsey’s account may have been compromised by an authorized third-party app rather than obtaining Dorsey’s account password.

However, this is not the first time that a high-profile account got hacked. Earlier, even Facebook CEO Zuckerberg’s account was hacked because his account didn’t use two-factor authentication with an easy-to-guess password.

Dorsey has 4.21 million followers on Twitter.