A PoC exploit for CVE-2017-9841 - PHPUnit Remote Code ... - GitHub
Vulnerable
If a project includes PHPUnit as a dependency (stored in the vendor directory) and that directory is publicly accessible via a web server, an attacker can send a specially crafted HTTP request to execute arbitrary PHP code on the server.
can identify if this endpoint is publicly accessible on your domain. a specific server, or are you trying to if a site is currently vulnerable to this? CVE-2017-9841 Detail - NVD
Despite being an older vulnerability, it remains a frequent target for automated scanners and botnets like because many legacy systems still have exposed /vendor directories.
Run composer install --no-dev to ensure development tools like PHPUnit are never deployed to production.