This is it. McDonald's SPECIAL SAUCE. As in "Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun."
Interested? It was released by a Canadian McDonalds. and HERE IT IS.
"...The chef pulls out a mixing bowl with mayonnaise, relish and yellow mustard. To it he adds a little white wine vinegar, garlic powder, onion powder and paprika "to enhance the color." A little whisking and voila -- special sauce..."