Hello, @mchiasson !
It is hard to say based on the information you are providing.
What do you mean by ".htaccess restrictions to block .ENV"? You should expose only the public folder and properly set the permissions for this folder. That is the most basic thing you can do.
Also, from a sysadmin point of view, relying only on a custom .htaccess configuration is a bad idea. You need to properly set up your web server (Apache or Nginx) to secure the Laravel root directory and only expose the public folder.
If the attacker has access to your vendor folder, he can use PHPUnit to trigger any PHP code via POST request.
I don't believe the problem is with PHPUnit however.
It is also important to upgrade your entire framework from time to time.
Hope this helps. Let me know.