Oh, was Rihanna on a Hawaiian vacation? I thought she was at Coachella Tweeting pics of herself looking amazing in a denim bikini. Anyhow, she was in Hawaii and she posted the Facebook pictures to prove it. We get it, she looks freaking banging in a bikini. Only problem: She accidentally posted one which exposed her nipple. Hey, it happens to the best of us sometimes. Click on to see the NSFW shot of Ri Ri and more celebs whose nipples have accidentally escaped their clothing. [Gossip Cop]
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