How does having the same password in different services make it less secure? How does having the same password as someone else make it less secure? Very basic question that I've always wondered about; I've been reminded by GitHub recently seen this message,
The password you provided has been reported as compromised due to re-use of that password on another service by you or someone else.
Generate a unique password for GitHub. If you use your GitHub password elsewhere and that service is compromised, then attackers or other malicious actors could use that information to access your GitHub account.
Theoretically, how would that work? Shouldn't a different salt render it almost useless to any attacker?
different salt values will create completely different hashed values, even when the plaintext passwords are exactly the same [Wikipedia]