Heidi Klum's naughty bare butt pic is her most risqué yet (PHOTO)

Sep 7, 2015 at 4:09 p.m. ET
Image: Ivan Nikolov/WENN.com

Heidi Klum must have been a very, very naughty girl this weekend, judging from the Instagram photo she just posted.

The supermodel isn't exactly shy when it comes to showing off her incredible body on social media, but this photo of her bare butt is her most risqué yet.

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The Project Runway star shared a close-up of her amazingly taut hindquarters — not too shabby for a 42-year-old mother of four — being spanked with "The Naughty Spoon," held by what appears to be a man's hand.

Two questions: What did she do that was so naughty, and whose hand is holding the spoon? Perhaps boyfriend Vito Schnabel's?

Tell us: What do you think Heidi Klum did that was so naughty?