The founder and chief executive of the Ashley Madison infidelity dating website, Noel Biderman, has stepped down.
A statement released by the firm said his departure was "in the best interest of the company".
The senior management team will take over leadership until a new chief executive is appointed, it added.
Details of more than 33 million accounts were stolen from the website, which offers people the chance to have an affair.
"We are actively adjusting to the attack on our business and members' privacy by criminals. We will continue to provide access to our unique platforms for our worldwide members," the firm's statement said.
"We are actively co-operating with international law enforcement in an effort to bring those responsible for the theft of proprietary member and business information to justice."
Canadian parent company Avid Life Media, which owns the site, has offered a reward of $C500,000 ($NZ585,000) for information about the Ashley Madison hackers.
The leaked data, stolen by a group calling itself Impact Team, also included 200,000 emails belonging to Noel Biderman.
Norwegian security researcher Per Thorsheim confirmed to the BBC that they appeared genuine.
"I saw one email or two emails and I could verify the sender, the recipient, the domains and everything so it has to be an email from the CEO's mailbox," he said.
"There's no doubt about that."
Mr Biderman, a former sports lawyer, launched the website in 2001.
He said at the time that he wanted to offer the same opportunities for both women and men seeking extra-marital encounters.
However some of the journalists and security experts who have trawled through the leaked data say there appear to be many more male profiles than female ones.
The site's name was made up of the two most popular names for baby girls in the US at the time - Ashley and Madison.
Parent company Avid Life Media also owns other match-making websites including Cougar Life, Established Men, and The Big and the Beautiful.
Prior to the hack, the firm had announced plans to list publicly in London later this year, with the aim of raising up to $NZ234m.
At the time Christoph Kramer, Ashley Madison's director of international relations, said Europe had "a more laissez-faire attitude" towards the sector.