A client/server product performs authentication within client code but not in server code, allowing server-side authentication to be bypassed via a modified client that omits the authentication check.
Client-side authentication is extremely weak and may be breached easily. Any attacker may read the source code and reverse-engineer the authentication mechanism to access parts of the application which would otherwise be protected.
Time of Introduction
Architecture and Design
Technical Impact: Bypass protection
mechanism; Gain privileges / assume
[REF-7] Mark Dowd, John McDonald
and Justin Schuh. "The Art of Software Security Assessment". Chapter 2, "Untrustworthy Credentials", Page
37.. 1st Edition. Addison Wesley. 2006.
Note that there is a close relationship between this weakness and CWE-656 (Reliance on Security through Obscurity). If developers do not believe that a user can reverse engineer a client, then they are more likely to choose client-side authentication in the belief that it is safe.