Cookie manipulation is a technique that allows an attacker to intercept, modify, or forge a cookie, which is a piece of data that is used to maintain the state of a web session. By manipulating the cookie, the attacker can hijack the session and gain unauthorized access to the web application. Known-plaintext attack, DoS, and SQL injection are not directly related to session hijacking, although they can be used for other purposes, such as breaking encryption, disrupting availability, or executing malicious commands. References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 6: Communication and Network Security, page 729; Official (ISC)2 Guide to the CISSP CBK, Fifth Edition, Chapter 4: Communication and Network Security, page 522.