Solve in 5 step:
step 1 : open a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.
step 2 : In the search box above the list, type or paste insec and pause while the list is filtered
step 3: Double-click the security.insecure_field_warning.contextual.enabled preference to switch the value from true to false
step 4: Double-click the security.insecure_password.ui.enabled preference to switch the value from true to false
Done.
Basics 