If you look carefully through your settings, you can disable this. I was getting porn through "friends of friends" and found a way to disable it.
Sorry it was too long ago for me to say exactly where it was, and I don't have time to dig through it all right now. But I do know that I've shut it
down on my profile & haven't had any pop up in a couple of years now.
Actually, last night my friend had to do a whole lot of defending when a Miley Cyrus porn showed up in everyone's screen. Sure, we know it's spam.
But the funny part is, he had to click on it first.
A whoooole lot of defending lol. Hacked he said lol. Suuuure you were.