If this file is left on a production server and exposed to the internet via an open directory index, anyone can send an HTTP POST or GET request containing PHP code to that specific URL. The server will receive it, pass it to eval() , and execute it as if the attacker were sitting at the server's keyboard.
The problem is not what the script does , but where it lives . This file resides inside the vendor/ directory, which in many misconfigured production environments is still accessible via the web root. index of vendor phpunit phpunit src util php eval-stdin.php
If an attacker can reach eval-stdin.php via HTTP, they can POST arbitrary PHP code to it. The script will evaluate that code, executing it with the privileges of the web server user. If this file is left on a production
Let’s decode the path: