According to the company, they've hired a security team to help them investigate the breach, informed the law enforcement, and are in the process of informing all affected users.
The leaked date includes personal information such as names, email addresses, encrypted (hashed) passwords, and data imported from linked networks when authorized by users.
The database that was breached also stored the questions, comments, answers as well as private messages.
Quora has logged out all affected users and reset the passwords for users that use password as an authentication method.
No social security numbers, credit card information or other extremely sensitive information were stored on Quora's databases.
Quora believes it has found the security hole but the investigation is still on-going.
We have discovered that some user data was compromised by unauthorized access to our systems. We've taken steps to ensure that the situation is contained and are notifying affected users. Protecting your information is our top priority. Read more here: https://t.co/uwbdMjoM1v-- Quora (@Quora) December 3, 2018