According to TMZ, these photos are from Bieber's grandmother's houses on Canadian Thanksgiving in October 2012. TMZ explains that Justin "thought he'd prank [his family] by grabbing his guitar and playing a naked set a la Jenny from Forrest Gump." Considering how these were taken at a family holiday celebration, the only question left is who, exactly, sold the photos to TMZ? Also, "WHY?" My eyes.
tmz.com