Hackers are focusing on vulnerabilities in the PHP web application development platform threatening 80% websites in the world. PHP has several predefined variables that are called SuperGlobals i.e. POST, GET, COOKIES, FILES etc. PHP applications do not protect against the modification of variables from external sources, such as query parameters or cookies. Imperva is particularly concerned about two vulnerabilities that can be used to execute code on servers running PHP and fail to stopparameter variables being modified.
Source: https://thehackernews.com/2013/09/thanks-to-php-superglobal-80-websites.html