Are you using the Sync service?

A detail like a website remembering you (log you in automatically) is stored in a cookie. You have to remove the Cookies from a website to make a website forget about you.

You can use these steps to make a website recognize and remember you:

• you can create an "Allow" exception to keep specific cookies, especially in case of secure websites and when cookies expire when Firefox is closed.
• Options/Preferences -> Privacy & Security -> Cached Web Content: "Clear Now": Exceptions

Note that Firefox stores cookies as part of session data when you leave tabs open when you close Firefox.

@the-edmeister No I'm not using the Sync service and never have.

@cor-el The problem is not that websites are remembering my credentials, I want it that way, why else would I let Firefox save them? The problem is I'm being logged in everywhere without being asked for my master password first, which it always did before.

If there is still a master password set then Firefox won't be able to enter a stored password until you have entered the MP once during the current session. You can check this by opening the Password Manager.

• Options/Preferences -> Privacy & Security: Logins: "Saved Logins" -> "Show Passwords"

You can cancel a MP prompt to logout (i.e. reset the MP for the current session).

If a website remembers you without entering a password then this is likely done via a special cookie like I wrote above. Using a 'remember me' cookie has nothing to do with having a password stored.

Well, as I mentioned in my first post, when I try to access all saved passwords in the firefox settings like you said, it does still ask for the master password as it's supposed to. The problem is, on those sites that I keep open permanently, I'm being logged in automatically without being asked for the master password. I mean, it's supposed to log me in automatically, that's exactly what I want, but only after I enter the master password. That's how it always worked until now, before this problem suddenly appeared.

If that's really the fault of some special cookie, how could I find out which one causes this behavior, and more importantly, how can I prevent it from happening again?

Can nobody answer my last questions?

You can modify this pref on the about:config page to prevent sessionstore from storing cookies.

• browser.sessionstore.privacy_level = 2
• 0:any; 1:non-HTTPS; 2:never;

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config