Following a report by Krebs on Security, Facebook acknowledged a bug in its password management systems that caused hundreds of millions of user passwords to be stored as plaintext in an internal platform, writes Lily Hay Newman.

Here is the link: https://www.wired.com/story/facebook-passwords-plaintext-change-yours/

You can find the report here: https://krebsonsecurity.com/2019/03/facebook-stored-hundreds-of-millions-of-user-passwords-in-plain-text-for-years/