Obscure master password

May be a glitch with cookies.
Try "Tools -> clear recent history" Tick all the checkboxes and select "All"...
Also don't forget to first verify whether you they (cookies) do ))

phishing? On the page of the hidden frame, leading to a page with http-authorization as auth-realm written the text "enter master password?" Although then it would be two fields for a username and password. So I think you need to restart FF in safe mode and check.

you have enabled the master password in firefox
\rtinyurl.com/3xvtd2x

The author, as it suggests to us

The master password is disabled.