credential stuffing is a cyberattack where the attackers take stolen credentials from one source, and try them across a wide variety of systems.
For example, if someone’s book club is breached and they login as sallyluvzbooks@gmail.com with a password of “Dickens1234!”, the attacker would try these against Gmail, Netflix, Spotify, and a number of others to gain additional access.
https://en.wikipedia.org/wiki/Credential_stuffing