Quora, the popular question-and-answer website, has suffered a massive breach.

On Friday, the company discovered that a mysterious attacker may have stolen name, email address and password data from 100 million users on the platform. "We've taken steps to ensure that the situation is contained and are notifying affected users," the company said on Monday.

If you've ever posted to Quora, but didn't want your identity revealed, don't worry. "Questions and answers that were written anonymously are not affected by this breach as we do not store the identities of people who post anonymous content," the company said in an FAQ about the incident.

Quora also made sure to hash and salt the password data, effectively scrambling the information into random characters and numbers. However, it isn't clear what hashing algorithm the company used and if it can be easily cracked.

Quora is still investigating what caused the breach, but it appears the hacker had access to most, if not all the data, ever posted on the question-and-answer website. This includes non-public information, such as user direct messages and downvotes.

Data imported from "linked networks" was also exposed to the hacker. This covers the "access tokens" or digital keys that can, presumably, allow someone to sign into Quora with their Facebook or Google account.

At the moment, it isn't clear if the hacker could've used these access tokens to pull data from other platforms. The company didn't immediately respond to a request for comment. In his breach notice, Quora CEO Adam D'Angelo noted: "The overwhelming majority of the content accessed was already public on Quora."

Nevertheless, he added that the breach was still a serious matter. Celebrities such as former President Barack Obama, Ashton Kutcher and director JJ Abrams all have verified accounts with the platform. Many business CEOs including Facebook's Mark Zuckerberg, also appear to have registered with the site.

In response to the hack, Quora has issued a password reset for all affected users, who should also be receiving an email notifying them about the incident. The company has also hired security firms and contacted law enforcement to help it investigate the breach.

To protect yourself, it's a good idea to make sure your old Quora password wasn't reused on another, important website. Hackers like to take stolen password information and use it to breach other accounts. Pilfered email address data can also be useful to email spammers and their phishing campaigns.

Quora has over 300 million monthly active users. But if you want to delete your account with the site, you can go here to learn how.