The Head, Footer and Post Injections plugin for WordPress is vulnerable to PHP Code Injection in all versions up to, and including, 3.3.0. This makes it possible for authenticated attackers, with Administrator-level access and above, to inject PHP Code in multisite environments.
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.