Are PHP SuperGlobals putting Web applications at risk?

In the newly published Imperva 'Hacker Intelligence Initiative Report' the in-the-wild modification and exploitation of PHP SuperGlobal variables has been investigated. This particular external variable modification weakness has been described as being where a PHP application does "not properly protect against the modification of variables from external sources, such as query parameters or cookies". Imperva has seen evidence of SuperGlobal variables being used as a launchpad for remote code execution, remote file inclusion and security filter evasions attacks.