Facebook warns users that account protection is ‘very low’ and asks them to give an extra email address. Facebook says it will give you back control of your account if you lose access to your account. But there’s no indication of what else Facebook might do with this alternative email address of yours. Facebook’s one-time password system does not guarantee 100% protection against hackers. But some users have the same password on their Facebook and email accounts – meaning that you could potentially lose control of both at the same time.
Source: https://thehackernews.com/2010/12/account-protection-status-warning.html