During the first round of AES CBC, the IV is xored with the first block.

Therefore if you xor the IV with `00000000000000090909090000000000`, the same ciphertext will decrypt to `access=0000`

```
$ nc 88.198.219.20 26739
Would you like to:
[1] Create a guest token
[2] Read the flag
Your choice: 1
{'token': '2476be04e156b2c3fc79af68d5839ad816bfa180e63deaaf18765d6e3a946f5988bb1303789f28cfa9eacd7f2eb816c1'}

Would you like to:
[1] Create a guest token
[2] Read the flag
Your choice: 2
Please enter your admin token: 16bfa180e63deaaf18765d6e3a946f5988bb1303789f28cfa9eacd7f2eb816c1
Please enter your token's initialization vector: 2476be04e156b2caf570a668d5839ad8
{'flag': 'ractf{cbc_b17_fl1pp1n6_F7W!}'}
```