View source for Firefox/Features/Form Autofill/Privacy & Security Considerations

Some things to keep in mind while working on form autofill relating to privacy/security:
* <input type=hidden>
* @hidden
* Fields hidden/obscured/off-screen
* @autocomplete=off
* attacks where the user is tricked into interacting with the autocomplete popup (e.g. clickjacking)
* security state of the page e.g. HTTPS vs. HTTP, invalid certificate, etc.
** Most relevant for payment information
* clickjacking on doorhangers
* Private browsing mode - don't save submitted info or touch storage metadata
* Integrate with Clear Recent History / Sanitizer?
* Don't save the CVV anywhere (including form history)
* Authentication: Re-prompt before showing plaintext
* Denial of service from large amounts of submitted data in forms