Hundreds of millions of Facebook and Instagram users’ passwords were stored in plain text for years on internal data storage systems. The issue was discovered by Facebook during a routine security review from January 2019, when they discovered that “some user passwords were being stored in a readable format”” The company says all the passwords are now masked and unreadable and that all the users who had their passwords stored. Facebook advises users to take the following measures to keep their account secure: Pick strong and complex passwords for all your accounts. Use a security key or two-factor authentication to protect your account using codes from a third party authentication app.”
Source: https://www.bleepingcomputer.com/news/security/facebook-employees-could-access-unencrypted-passwords-for-millions-of-users/