Firefox/Features/Web Payments/Privacy & Security Considerations

Some things to keep in mind while working on Payment Request relating to privacy/security:

• avoid leaking the user's shipping address before payment (as much as possible) while still allowing shipping option calculations (both shipping methods and shipping availability)
• navigations away from a page showing a Payment Request dialog should either be prevented or the dialog should abort.
• attacks where the user is tricked into interacting with the Payment Request dialog (e.g. clickjacking)
  • The pay button should probably have a security delay
• security state of the page e.g. HTTPS vs. HTTP, invalid certificate, etc.
  • Only allowed on secure contexts. Should we disable for cert overrides? What about for developers?
  • Most relevant for payment information
• Private browsing mode
  • default to not saving new addresses
  • don't update storage metadata
  • don't leak the user's shipping address without clear understanding
  • don't remember the last used address for the site
• Integrate with Clear Recent History / Sanitizer?
  • N/A for basic-card
• Don't save the CVV anywhere (including form history)
• Master password: Require entry before every use of the plaintext card number
• Spoofing issues from showing page generated strings in a privileged dialog
  • e.g. we should constrain the amount of space that the untrusted strings can take on the screen and handle special characters e.g. whitespace and new lines carefully
• Handle abusive pages repeatedly showing a payment request dialog (e.g. holding the user hostage until they pay).
  • The proposed design will allow the user to close the whole tab while the dialog is open
• What happens if the dialog appears during DOM or UI fullscreen?
• What happens if the dialog appears in different variants of popup windows? (consider window.open features)