Hello, Firefox actually stores the entire card number and expiration date. It does not autofill this until you use the cvv, which Firefox does not store. The last four digits are shown because they are a fingerprint of the card, and therefore can be used to identify the card. If you would like to stop credit cards from being stored, you need to use about:config. <i>'''WARNING from the moderator team:''' Changing Firefox pref from the about:config page can sometimes break Firefox or cause strange behavior. You should only do this if you know what you're doing. Please read [[Firefox Advanced Customization and Configuration Options]] to learn more. </i> '''extensions.formautofill.creditCards.enabled''' => '''false''' '''extensions.formautofill.creditCards.available''' => '''false'''

See also: *https://support.mozilla.org/en-US/kb/credit-card-autofill *https://support.mozilla.org/en-US/kb/automatically-fill-your-address-web-forms