Twitter on Friday said that its co-founder and Chief Executive Officer Jack Dorsey’s account on the microblogging site was hacked after a series of offensive messages were posted, BBC reported. The platform later claimed that it had regained control of the account that “been compromised” and that they were investigating the episode.

“The account is now secure, and there is no indication that Twitter’s systems have been compromised,” Twitter said. “The phone number associated with the account was compromised due to a security oversight by the mobile provider. This allowed an unauthorized person to compose and send tweets via text message from the phone number. That issue is now resolved.”

The messages, some of which were posted directly from Dorsey’s account and some retweeted from other accounts purportedly made anti-Semitic remarks with reference to the Holocaust. Another post said that there was a bomb at the social networking site’s headquarters in San Francisco.

A chat channel on Discord, a different website, was reportedly set up by the group of hackers to discuss and joke about the hacking, but it was immediately shut down. The hackers had control of the Twitter co-founder’s account for about 15 minutes when they sent out a flurry of tweets.

Twitter also suspended the accounts whose offensive posts the hackers retweeted from Dorsey’s account and suspended the one that was seemingly responsible for the cyber attack, according to Associated Press.

A group, called the Chucking Squad, said that it was behind the breach. However, apart from getting some accounts unsuspended, the group had not said why it decided to hack Dorsey’s account.

Hackers have learnt how to get around the two-step verification for accounts. Twitter refused to comment when asked if its CEO had used a two-factor login for his account.

This is not the first time the Twitter CEO’s account was hacked. In 2016, Dorsey’s account was taken by hacker group OurMine, which had also attacked other high-profile accounts including Facebook CEO Mark Zuckerberg. The episode came after Twitter and Dorsey recently asserted that it would improve the health and civility of discussions on the platform.

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