Answered by Shaykh Faraz Rabbani
Is it permissible to pray behind a Wahhabi/Salafi?
Yes. Ibn Abidin mentions that it is somewhat disliked to pray behind the people of bid`a, but doing so is superior to praying alone. If possible, it is superior, of course, to pray behind someone whose practice there is no question about.
Wassalam,
Faraz