If you need your credit card number but don't have your card nearby, you can retrieve it from Mozilla Firefox if the browser has saved it for you with Autofill in the past. Here's how.
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First, open Firefox on Mac, Linux, or Windows. In any window, click the menu button (three lines) in the upper-right corner, then select “Preferences” (on Mac) or “Options” (on Windows and Linux).
When the “Preferences” or “Options” tab appears, click “Privacy & Security” in the sidebar menu.
Then, scroll down to the “Forms and Autofill” section and click the “Saved Credit Cards” button.
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In the window that appears, Firefox will display a list of all the credit cards it has saved. Select the card for which you want to see the number and click “Edit.”.
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Tip: If the “Saved Credit Cards” list is empty, then Firefox has not saved any credit card numbers.
In the “Edit Credit Card” window, you will see the full credit card in the “Card Number” box. If the expiration date and name on the card have been saved, they will also be listed.
Please note that Firefox will never store the three- or four-digit card security code (often called the “CVV number” or “CSV number”) found on the front or back of your credit card. To obtain it, you will need the card itself.
If you want to remove a credit card from Firefox, click “Cancel” to return to the main card list, then select a card and click “Delete.” Firefox will immediately delete the saved card information
Information source: howtogeek.com
