When deploying via Composer, always use the --no-dev flag (e.g., composer install --no-dev ) to ensure testing tools like PHPUnit are never installed on live servers.
PHPUnit is a fantastic piece of software—for testing . But its presence on a public-facing server represents a catastrophic failure of deployment hygiene. The code inside eval-stdin.php is arguably the most dangerous 79 characters in modern PHP history, because it gives an attacker exactly what they want: a direct pipeline from HTTP to eval() . vendor phpunit phpunit src util php eval-stdin.php exploit
If you run composer install without --no-dev on a public server, you are effectively inviting attackers to execute any code they wish. The fix is simple: Use .gitignore for vendor/ on the build side, and never, ever let phpunit touch your production web root. When deploying via Composer, always use the --no-dev flag (e
curl -X POST https://target.com/vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php \ -d "<?php system('id'); ?>" The code inside eval-stdin
The most robust defense is preventing web access to internal PHP files.