They'll get the XOR of the two original messages, and also can break authentication: https://crypto.stackexchange.com/questions/26790/how-bad-it-is-using-the-s

They'll get the XOR of the two original messages, and also can break authentication: https://crypto.stackexchange.com/questions/26790/how-bad-it-is-using-the-same-iv-twice-with-aes-gcm/68525#68525 https://crypto.stackexchange.com/questions/26790/how-bad-it-...