Are you sure it isn’t working? That said, a master password is only used for viewing and (Firefox) getting access to stored passwords, not to prevent regular browsing (see this support article). Are you saying you are able to log in somewhere using a stored password, or view them in the Saved Logins?

I must say mostly I can't get access. I'm restoring session and I have tabs with logged sites which I can access (like mail, fb, yt) without pop-up shown and on some (kongregate in that case) pop-up shows and I can cancel it but I'm logged. But when I go to site where I haven't log for some time it works as supposed to (it doesn't autocomplete password). Also in options I can't turn off master password nor view them in saved.

I tried safe mode - without success. Then I try private mode (I tried it before) and what was surprising when I type my master password in pop-up it worked. But when I tried to turn it off in options, it didn't work. I tried private again, and it didn't work (private+safe also).

If you use firefox browser and have an Firefox account you HAVE TO use a master password. Firefox will automatically check this setting. If you choose not to have a master password you still have to remove the message asking for it several times during an internet session. It is NOT OPTIONAL. Because of this I'll remove my account and start using another browser.

For what I can see, the behavior you described is as it should, since you can’t view any stored passwords without re-entering the Master password.

As for restored sessions that allow reloading the page without entering the Master password (even when Firefox is asking for it): I’m afraid this depends on the website. In other words, the ability to log in can depend on a (temporary) token or cookie only, and users would not be able to influence that other than by waiting for a while or clearing cookies manually or automatically when closing Firefox (which you can probably verify). This may also explain any recent change in behavior for some websites, since website owners can use and change methods whenever they want.

Therefore it’s probably safest for users to log off from any website prior to closing a browser. Perhaps making Firefox not remember cookies (set it to "Never remember history" or "Use custom settings for history" and appropriate cookie settings) might suit your needs as well.

This has nothing to do with the most recent post above (if it hasn’t been removed) referring to Sync and Firefox Accounts.

Thanks, will take a look at your answer later.

if you want use master password, you should use firefox sync. I hard reset master password and then use sync to restore almost all (or maybe all) my passwords.