Rating:

tldr;
- the three ciphers are AES-ECB, AES-CBC, AES-CFB
- security of the keys are 24 bits each
- AES-CFB is a stream cipher that encrypts/decrypts data by by encrypting an IV with AES, then XORing the result with the plaintext/ciphertext
- firstly, obtain a plaintext/ciphertext pair $(p, c, IV_1, IV_2)$
- next, guess the 2^24 possible keys and ask the oracle to decrypt $(c \oplus E_{k_3}(IV_2) \oplus E_{k_3}(r), IV_1, r)$ for some arbitrary $r$
- if the key guess is correct, the result will be the same as our original plaintext $p$