When a stream cipher like RC4 is used twice with the same key, it becomes vulnerable to a ciphertext-only attack. In this type of attack, the attacker has access to several ciphertexts that are encrypted with the same key but does not know anything about the plaintexts. By analyzing these ciphertexts, an attacker can gain insights into the plaintext or even recover parts or all of it. References := Cisco Cybersecurity source documents or study guide (I need to search for specific references as I don’t have direct access to Cisco’s proprietary content)