Permissions, Privileges, and Access Controls
The Piwik_Common::getIP function in Piwik before 1.1 does not properly determine the client IP address, which allows remote attackers to bypass intended geolocation and logging functionality via (1) use of a private (aka RFC 1918) address behind a proxy server or (2) spoofing of the X-Forwarded-For HTTP header.
CWE-264 - Permissions Privileges and Access Controls
CWE 264 (permissions, privileges, and access controls) is not a weakness in and of itself, rather it is a category of weaknesses related to the management of permissions, privileges, and other security features used to perform access control. If not addressed, the weaknesses in this category allow attackers to gain privileges for an unintended sphere of control, access sensitive information, and execute arbitrary commands.