The essence of the Credential Stuffing problem centers around the fact that lots and lots of user credentials have been stolen from many different places. An attacker will take stolen credentials from one place and try to "stuff" them into another in order to gain access. The problem (other than the fact that credentials were stolen) is that many people use the same username and password on multiple web applications. This video discusses the issue of credential stuffing and offers solutions to avoid this problem. Enjoy!