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Ignoring MD5/image format-specific collision realities, theoretically an attacker could submit a contraband image that collides with a valid, allowed image they may want to remove.

When action is taken on the first image, the collided image could also be censored.

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Not with current technologies. There is a big difference between creating an image that collides with a specific target hash and just making two images that collide when you control both. The former is not currently possible, and the latter is.

That being said, you could probably create a pair of colliding images, give one to a news outlet or something, then later post the second (presumably banned) one. The app would on short notice need to decide between banning neither or banning both.

> That being said, you could probably create a pair of colliding images, give one to a news outlet or something, then later post the second (presumably banned) one. The app would on short notice need to decide between banning neither or banning both.

Yeah they did this - except the contraband was automatically recognised and both images were banned via hash.

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