Firefox contains a ton of privacy features that help to keep our users' data secure. If you go to the Privacy tab in the Firefox Options page, you can find the settings relating to your history, search data, etc.

If you select Use custom settings for history, you will have full control over what Firefox does with your history. You can uncheck all of the history that you do not want Firefox to remember (browsing history and form/seach in your case). You will also have control over how long Firefox stores cookies and can even prevent Firefox from saving cookies at all.

If you select to Clear history when Firefox closes, you can tell Firefox to dump your history each time you close the browser. If you click the Settings... button corresponding to this option, you will have total control over what history Firefox deletes when you close Firefox.

If you would like to delete your existing saved form autocomplete results, simply click on the text field in which the form data displays, hover over the entry that you wish to delete and press the delete key on your keyboard. Alternatively, you can install the Form History Control addon on your browser for a wider range of settings and control relating to the form history.

I hope this is the information that you were looking for. Please let us know if you require more information or assistance.

Solved my problem. Thanks.

No problem. Glad that I could help. Thanks for contacting the Mozilla support team.