Information
Firefox allows for credentials to be stored in its credential store for certain websites.
Rationale:
Stored credentials may be harvested by an adversary that gains local privileges equal to or greater than the principal running Firefox, which may increase the scope and impact of a breach. However, preventing Firefox from storing credentials will not prevent such an adversary from harvesting credentials used while compromised.
Impact:
Credentials will not be stored for websites.
Solution
To establish the recommended configuration, set signon.rememberSignons to false:
Type about:config in the address bar
Type signon.rememberSignons in the filter
Ensure the setting is set as prescribed.
OR
Open the mozilla.cfg file in the installation directory with a text editor
Add the following lines to mozilla.cfg:
lockPref('signon.rememberSignons', false);
Default Value:
True (Enabled).