https://support.mozilla.org/kb/Forgot+my+master+password Resetting your master password will remove all of your saved usernames and passwords. This is a security feature. Type chrome://pippki/content/resetpassword.xul<Enter> in the address bar.

The master password is used to encrypt and decrypt the usernames and passwords in the Password Manager. When you do not know the MP then you won't be able to modify the existing MP and your only option to reset the MP will remove (invalidate) all saved passwords. You can keep a backup copy of logins.json and key3.db in case you want to give it another try in a second profile.

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

In the event that the passwords information is lost, you should record all information in a separate text file somewhere else on your hard drive, or written down. You can easily copy and paste if you need to do so. If you are concerned about someone else looking at that file, you can compress it using a password.

Recently (since Nov 2017) Firefox shows a box requesting password info on every site I visit. I don't want a Master Password. I don't want Firefox to remember passwords. I never asked Firefox to remember passwords. I will have to stop using Firefox if this box appears on every site I visit.

Just turn off the Password Manager.

Type about:preferences#security<enter> in the address bar. Note: For Firefox 56+ its; about:preferences#privacy

Under Logins, Turn on or off Remember Logins. To check the passwords you have listed, press Saved Logins.