CALIFORNIA: Question-and-answer website Quora said on Monday (Dec 3) its user data had been compromised, with about 100 million users affected by the security breach.
The breach was discovered last Friday, after a "malicious third party" gained unauthorised access to one of their systems, CEO Adam D'Angelo said in a blog post.
Users' account information, including names, email addresses, encrypted passwords and data imported from linked networks when authorised by users may have been compromised, he said.
The breach did not affect questions and answers that were written anonymously.
The company said it is in the process of notifying users whose data have been compromised. Potentially affected users have been logged out and their passwords invalidated.
It also said that the root cause has been identified, with steps being taken to address the issue. Law enforcement has been notified, it added.
"We have retained a leading digital forensics and security firm to assist us," Mr D'Angelo said.
"While the investigation is still ongoing, we have already taken steps to contain the incident, and our efforts to protect our users and prevent this type of incident from happening in the future are our top priority as a company."
The Quora Inc-owned website was founded in 2009 by Mr D'Angelo and Mr Charlie Cheever, two former Facebook employees.