Twitter has said its investigation uncovered an operation that targeted Twitter employees to gain access to internal systems and tools.
The attackers gained access to dozens of high-profile accounts, including those of Apple, Amazon CEO Jeff Bezos, Microsoft founder Bill Gates, Joe Biden and former President Barack Obama.
Twitter shares sank Thursday, a day after hackers gained access to more than a dozen high-profile accounts, including those of Jeff Bezos, Bill Gates, Joe Biden, former President Barack Obama, Elon Musk and the corporate account of Apple, CNBC reports.
The accounts displayed tweets telling followers to send bitcoin to a specific address.
Share prices were down more than 5% in Thursday's premarket.
Musk was the first hacking victim Wednesday when a tweet was posted early in the afternoon on the Tesla CEO's account promising to double any payments sent to a bitcoin address.
Twitter said late Wednesday its investigation uncovered an operation that targeted Twitter employees to gain access to internal systems and tools.
"We detected what we believe to be a coordinated social engineering attack by people who successfully targeted some of our employees with access to internal systems and tools," the company tweeted from a support account.
"We know they used this access to take control of many highly-visible (including verified) accounts and Tweet on their behalf."
Twitter CEO Jack Dorsey said that the company feels terrible about the hacked accounts.
Other accounts hacked included former New York City Mayor Mike Bloomberg, musicians Kanye West and Wiz Khalifa, Berkshire Hathaway Chairman Warren Buffett, reality TV star Kim Kardashian, the Cash App corporate account, and Uber's corporate account.
The bitcoin-related tweet was Apple's first-ever tweet, although the account had placed ads in the past.
Rachel Tobac, CEO of cybersecurity firm SocialProof Security, told NBC News the attack was likely the most significant Twitter had ever seen.
"We are lucky the attackers are going after bitcoin (money motivated) and not motivated by chaos and destruction."