Twitter had to assure employees that Elon Musk's infamous late-night email about his 'hardcore' vision for the company wasn't a phishing attack, report says

• Elon Musk emailed Twitter staff this week saying they must commit to his 'hardcore' vision for the company.
• Failing to do so by 5 p.m. ET on Thursday meant they'd receive three months' severance, he said.

Twitter had to assure employees that Elon Musk's infamous late-night email asking them to commit to his "hardcore" vision for the company wasn't a phishing attack, The Wall Street Journal reported Thursday.

Earlier this week, Musk emailed Twitter staff saying the company would need to be "extremely hardcore" to "build a breakthrough Twitter 2.0" and employees needed to commit to his vision by 5 p.m. ET on Thursday — or they'd "receive three months of severance."

The lack of detail in his short email created confusion in Twitter's ranks, forcing the company to respond with a document answering employees' questions, The Journal reported.

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The document stated that Musk's email should be regarded as an official company communication and said: "This is not a phishing attempt," per The Journal.

The document said: "As you have seen, Twitter is at the beginning of an exciting journey. We are asking you to confirm that you want to be part of this journey."

Twitter didn't immediately respond to Insider's request for comment, made outside normal US operating hours.

The email sent by Musk said employees who wished to remain at Twitter would need to work "long hours at high intensity," adding: "Only exceptional performance will constitute a passing grade."

Fewer than half of Twitter's workforce chose to stay at the company after Musk's deadline passed Thursday, Insider's Kali Hays reported.

As the deadline passed, Twitter temporarily closed its offices, banning staff from entering its buildings until Monday.

Employees who declined to commit to Musk's vision by the Thursday deadline said they still had access to internal company systems such as email and Slack.