PERSON A sends messages to PERSON B using AES, CBC, PKCS5Padding with an IV that is incremented by one after each message. If PERSON Z knows that the first block of the plain-text of any message is either "Yes" or "No", can she launch an attack that decrypts the first block of a given message? Hint: Chosen Plaintext Attack
My answer is I do not think it is possible to mount an attack that decrypts the first block because of the avalanche effect. Any changes, whether if it is the size or the content, atleast 50% of the content in CT changes.
Is there anything missing or totally wrong in my answer??