Facebook has removed the built-in login dialog for security reasons. However, if the user has logged into Facebook but has not yet allowed your application, a pop-up window asking you to allow your application will be built-in. However, everything that asks for the Facebook password will be displayed in a pop-up window so that the user can see the URL of the site that receives its password. It gives the user peace of mind.
I tried to understand why mine changed for me, but it is not. The built-in block is displayed for registered users who have not previously used your site / application. An FB user not connected to Facebook will receive a popup.
Geoff
source share