They used a spatula to swirl the icing round the cupcake!
That looks like it was iced with a spatula to me.
Here's a video on how to:
No tip. Just a spatula and a swift movement of your hand. There are lots of movies showing the technique on YouTube. I'm on my phone right now so I can't give you links but if you google it, you'll find it.
Sorry it's the mini cupcake I was wondering about - if you scroll through them until you get to the vanilla bean mini cupcake, I don't know how to post a link directly to it.
I think the OP is refering to the mini cupcakes...it looks to me like it COULD be a Wilton 6B or 8B...something along those lines
I think is a 6B or 8B too.
Thanks for your help.