I'm not a teacher or grammarian so I'm not sure about the formal grammar. I think of it as a shortening of "a prank which has gone wrong." And I think of "wrong" as short for "in the wrong direction." If you try to do A, and instead B happens, and B is bad, a mess, a catastrophe--then A "has gone wrong." We can think of a scale: something "went well," or "didn't go well," or, worst of all, "went wrong." "How did your camping trip go?" "It went well, we had a great time." "How did your camping trip go?" "It didn't go well, it rained a lot and there were swarms of mosquitoes." "How did your camping trip go?" "Everything went wrong. The air mattress went flat, we forgot to bring propane for the camp stove and couldn't cook anything, and the car broke down."

I can't give you a proper answer, but it's not the passive voice. You can't really say "Halloween prank gone wrong by trick-or-treaters". Just as much as you can't say "Trick-or-treaters gone wrong Halloween prank". It doesn't make any sense. Maybe I'm overlooking something, but I think it's just "newspaper headline speak" for "The Halloween prank that has gone wrong". And why? Because it's short and sounds catchy. Edit: originally I also thought it might be an adjective, but you can't really say "The Halloween prank is gone wrong".

Hello, it is a form of "to go" (past participle), acts as adjective here. Examples: The prank did not go well. Our prank has gone well so far. Prank gone wrong How will the prank go? Hope that helps, Martha