On Friday, Jeremy Burge, who runs the website Emojipedia, posted a tweet claiming numbers added to use two-factor authentication – a secure login process requiring two steps before accessing an account – were now searchable.
"For years Facebook claimed ... adding a phone number for 2FA was only for security. Now it can be searched and there's no way to disable that," Burge wrote.
Burge said Facebook sets its default for phone number search to everyone, and there's no way to fully opt out.
When a user signs up for two-factor authentication, they provide additional information to confirm their identity, such as a phone number or email address. In the case of Facebook, they can use a phone number to text a security code users must type after they log in to confirm their identity. Typically, phone numbers provided for this don't appear on user profiles.