The number being somewhere on your computer isn't something I'd worry about. The real risk is from a liberal autocomplete that might throw it into website forms where you don't want it to be, including hidden ones. Maybe there are protections in place since I last let Firefox save anything like this, but it used to try pasting address and CC info whenever it could.
The number being somewhere on your computer isn't something I'd worry about. The real risk is from a liberal autocomplete that might throw it into website forms where you don't want it to be, including hidden ones. Maybe there are protections in place since I last let Firefox save anything like this, but it used to try pasting address and CC info whenever it could.