A safety is now possible for either team and will be worth 1 point. Rule 11-3-2-c states, "If the try results in what would ordinarily be a safety against either team, one point is awarded to the opponent."

In the past in the N.F.L., if an extra point was blocked, the ball was declared dead if a defender got hold of it. Under the new rules, he can try to return it, possibly all the way for a [safety], which would be worth 2 points.

Perhaps a defensive player recovers the ball in the field of play, and while returning it he retreats into the end zone and is pulled down there. That will be a 1-point safety for the kicking team.

https://www.nj.com/giants/2015/09/how_the_nfls_new_extra_point_rules_have_created_a.html