Jennifer Lawrence Jennifer Lawrence

Nude photos of Jennifer LawrenceAriana Grande and numerous other celebrities were posted online Sunday following a massive hack into Apple's iCloud storage system.

Lawrence's publicist verified that the photos are her, telling Buzzfeed: "This is a flagrant violation of privacy. The authorities have been contacted and will prosecute anyone who posts the stolen photos of Jennifer Lawrence."

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The leak has been traced back to a user on a 4chan message board, who also claims to have video of Lawrence engaged in sexual acts, according to Buzzfeed.

Other celebrities involved in the hack include Grande, RihannaKim KardashianKate Upton and Aubrey Plaza, according to a "master list" that has been circulating online. Some stars, including Victoria Justice, are claiming that the pictures are fake, however.

"These so called nudes of me are FAKE people. Let me nip this in the bud right now. *pun intended*," Justice tweeted Sunday.

But others are admitting they're real. Actress Mary Winstead tweeted: "To those of you looking at photos I took with my husband years ago in the privacy of our home, hope you feel great about yourselves."