Yup. Changing your password or 2FA wouldn’t help here, because they’re not actually logging into your account. Rather, they’re simply telling the server that they’re already logged in, using your auth token as proof. You know that little “Keep me logged in” checkbox that everyone clicks when they log in? That stores an auth token on your browser, which is tied to your account.

The next time the browser starts a session on the site, it sends that auth token instead of going through the regular login process. And since the site knows that auth token belongs to your account, it logs you in automatically without needing to go through the regular login process.

So basically, they’re stealing a cookie from your browser, with your name on it. Then they’re able to tell the server that they’re you, by presenting that cookie as proof.

Proper procedure should be to deauthorize any auth tokens when you change your password. But even big sites get lazy about this sometimes, so it may not be the default. If this is the case for Lemmy, even changing your password won’t help because it doesn’t automatically deauth that token.