"We have retained a leading digital forensics and security firm to assist us", Mr D'Angelo said.
Anonymously authored questions and answers were reportedly not affected by the breach, and the company said it doesn't store information from anonymous users.
That's because to access a Quora page, you have to log in - either by creating an new account or by linking your Google or Facebook account.
"We are notifying affected Quora users", the statement said.
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.
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"Quora is unique in that sense, it's a tech company from the grounds up headquartered in the Silicon Valley having around 300 Million monthly active users".
The breach comes only days after the database of Marriott International, the world's largest hotel company, was hacked, affecting about 500 million records from its Starwood Hotels reservation system, exposing personal data of customers that included some payment card numbers.
Current actions being taken by Quora include notification of the compromised users, and logging out all Quora users who may have been affected and an invalidation of their passwords.
For users of Quora, the company advised that they change their password - if they were using their Quora password across multiple services. Quora only described the attackers as a "malicious third party", although they have also mentioned that they've "identified the root cause". Those wishing to delete their account can do so in the settings section and the deactivation will happen immediately. And, if you used the same password for any other services, I'd be changing those too. "We have already taken steps to ensure the situation is contained, and we are working to prevent this type of event from happening in the future". "We have notified law enforcement officials".