Use NMAP to identify the target machine (192.168.4.1) among (192.168.4.0/24)
Use NMAP to identify the service: port 8080/TCP
Discover the vulnerability: the same key is simply XORed with the plaintext for all encryptions
Encrypt a custom plaintext
Retrieve the ciphertext from /show_encrypted_notes
Recover the key: XOR the plaintext with the cyphertext: ebd2df76aac328081c10a48e91f848fbdf6edb15fa680ba1fec52e070a8ca81b9bc9110af8732af92bf3f39e48b0b45208a78f1b6efc691b1c991f828943d025
Decrypt the flag
Use the FinalAnswer tool