The attacker sends a POST request. The body of the request is the PHP code they wish to execute.

If the server is vulnerable, the response body will contain the output of the id Linux command (e.g., uid=33(www-data) gid=33(www-data) groups=33(www-data) ).

If the file is present and accessible, the scanner notes the target.

An attacker who discovers that a target website has the PHPUnit eval-stdin.php file publicly accessible can exploit it with a simple HTTP request:

In the modern landscape of PHP development, dependency management via Composer is the industry standard. It powers frameworks like Laravel, Symfony, and WordPress plugins alike. However, the convenience of composer require comes with a hidden cost: the security of your application is only as strong as the weakest link in your supply chain.

Shortly after the CVE was published, mass-scanning tools and automated bots began hunting for /vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php . Exploitation attempts included:

If you meant to ask something else (like how to run PHPUnit tests correctly), please rephrase and I’ll help with that instead.

curl -X POST \ -d "<?php system('id'); ?>" \ https://target-site.com/vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php

Attackers use automated bots to scan the internet for the specific path. They look for servers that return a 200 OK status code when requesting:

If an attacker sends an HTTP POST request to https://your-site.com/vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php with a payload in the request body, the server will:

Many developers ran composer install --no-dev locally but forgot to use --no-dev in CI/CD pipelines meant for production. Worse, some would simply git add vendor/ and push everything to production.

: The script runs instantly when accessed over HTTP, requiring no cookies, API tokens, or login sessions.

: The script passes the raw input stream directly into the dangerous eval() statement.