The extraordinary hacking spree that hit Twitter - targeting some of the most high profile accounts - is drawing urgent questions about the platform's security and resilience.
The company said late Wednesday that hackers took control of employee credentials to hijack the accounts of some of the most prominent political and business figures in the U.S. - from Barack Obama and Joe Biden to Bill Gates and Warren Buffett.
In a series of tweets, the company said: “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 statement confirmed the fears of security experts that the service itself - rather than users - had been compromised.
Posing as celebrities and the wealthy - those responsible for the attack asked followers to send bitcoin to a series of addresses.
Mikko Hypponen, a cyber security expert says what the hackers chose to do with their access - tells us a lot about who they could be.
"They could do anything on Twitter, but they chose to use these quick hack mechanisms of making a little bit of bitcoin. They could have sold this access to a number of places, for example, to foreign intelligence agencies. They could have used this access to announce a merger and acquisition in the name of Bill Gates or Elon Musk, which would have immediately affected stock prices. ..This was most likely an opportunistic hack, most likely done by some younger people. And this was the first thing they could imagine - is to make some money."
Wednesday's hack - the worst to date for Twitter - is also raising questions about Twitter's resilience in the run up the the U.S. presidential election.
Its role as a key communications platform for politicians and public officials - including President Donald Trump - has led to fears hackers could wreak havoc with the November election or otherwise compromise national security.
After the day's chaos - Twitter CEO Jack Dorsey said "Tough day for us at Twitter. We all feel terrible this happened."