"None of this should have happened, and I will not make excuses for it", Khosrowshahi wrote.
If you are one of the 40 million riders who use Uber every month, the company encourages you to keep an eye on your credit and any fraud alerts as well as monitoring your Uber account for unusual activity.
The stolen information included names, email addresses and mobile phone numbers of Uber users around the world, and the names and license numbers of 600,000 U.S. drivers, Mr Khosrowshahi said.
"We are changing the way we do business, putting integrity at the core of every decision we make and working hard to earn the trust of our customers".
He says the hackers went into a coding site, called Get Hub, and allegedly impersonated Uber engineers. Uber is also being investigated in the United Kingdom for the data breach, because the island nation is the largest Uber user in Europe.
Uber waited until Tuesday to begin notifying the drivers with compromised driver's licenses, which can be particularly useful for perpetrating identify theft.
"Cloud services, such as AWS, are secured with SSH [secure shell] keys that are often outside the control of security teams", said Kevin Bocek, vice-president of security strategy and risk intelligence at Venafi.
And while this data breach is startling at the very least, the way the company handled it is even worse. Uber said it believes the information was never used but declined to disclose the identities of the attackers.
Uber has admitted it covered up a data breach in 2016 that affected 57 million customers and drivers.
"They've stopped it, they took care it, I'm still gonna drive", said Uber driver Bobby Bennett. Earlier in January this year, Uber was fined US$20,000 for failing to disclose a comparatively less serious breach in 2014.
Uber's payoff to prevent hackers from leaking the stolen data is more similar to recent extortion attempts on Netflix and HBO than ransomware campaigns.
Amy Spitalnick, spokeswoman for Attorney General Eric Schneiderman, confirmed the probe Wednesday, but would not comment further.
Khosrowshahi says "two of the individuals who led the response to this incident are no longer with the company". Fifty-seven million people is a significant chunk of Uber's user base, which hit 40 million monthly active riders past year.
"This wasn't simply a data breach", Rubin said.
Regulators in Australia and the Philippines said they would look into the matter.
Mr Sullivan, formerly the top security official at Facebook and a federal prosecutor, served as both security chief and deputy general counsel for Uber. The company has been embroiled in a number of controversies, including using software called Greyball to evade regulators, a court battle over allegedly stolen secrets from Google's self-driving auto division, and a slew of complaints regarding sexual harassment and toxic company culture.
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