The system must encrypt and verify client-side session information (ViewState).
CWE-642: External Control of Critical State Data. The software stores security-critical state information about its users, or the software itself, in a location that is accessible to unauthorized actors.
OWASP Top 10 A2:2017-Broken Authentication. Application functions related to authentication and session management are often implemented incorrectly, allowing attackers to compromise passwords, keys, or session tokens, or to exploit other implementation flaws to assume other users' identities temporarily or permanently.
PCI DSS v3.2.1 - Requirement 6.5.10 Address common coding vulnerabilities in software-development processes such as broken authentication and session management.