Photo: Rihanna flashes under-boob

Forget side-boob, side-boob is out. It’s all about the under-boob now.

Rihanna was flashing ever so slightly during a recent performance at Wireless Festival in Hyde Park, London.

Click here for a photo.

Click here to see more wardrobe malfunctions from the likes of Miley Cyrus (queen of the side-boob) and The Saturdays, because Frankie Sandford and her bra, they got issues.