On Saturday hackers broke into Jack Dorsey’s account. The micro-blogging platform later said it secured the account of Dorsey that became the victim of’ SIM swapping’ or’ SIM jacking’ where a mobile number is moved to a fresh SIM card.

A group of hackers called ‘ Chuckling Squad ‘ stated it was behind Dorsey’s cyber-attack with over 4 million supporters. By taking control of Dorsey’s number, hackers posted tweets via text messages on his Twitter account.

“The phone number associated with the account was compromised due to a security oversight by the mobile provider. This allowed an unauthorised person to compose and send tweets via text messages from the phone number,” Twitter said in a statement.

According to TechCrunch, one of the tweets posted a Twitter handle of someone who purported to take credit for the account takeover. That account was immediately suspended.

“We’re aware that @jack was compromised and we are investigating what happened,” said Twitter.

The tweets appear to have come via Cloudhopper, a company that Twitter previously acquired to help with its SMS service, reports The Verge.

The hacker seems to be from the same group that last week on Twitter assaulted YouTube celebrities, including beauty vlogger James Charles, Shane Dawson, and comedian King Bach.

In 2016, the security firm OurMine hacked Dorsey’s handle to send out a message about “testing your security.”

OurMine also hacked the accounts of Facebook CEO Mark Zuckerberg and Google’s Sundar Pichai. The accounts of Zuckerberg on both Twitter and Pinterest were compromised.

The hacker group ‘OurMine’ claimed that it was possible due to the LinkedIn password dump. Millions of LinkedIn user account details were leaked online in 2016.