Removed: This hook was removed in version 3.0 with no replacement.
No parameters are passed to this event; however, it is useful to note that the GFUser object is a global namespace and properties can be safely added to it from this event.
This event is useful when wishing to add or modify values in the GFUser object. In the below example you can see how to add two values to the GFUser object and then call another function that process these new properties.
This filter is located in userregistration.php