HSC MailInspector v5.3.3-7 contains a Local File Inclusion (LFI) vulnerability caused by improper control of user-supplied file paths. The endpoint /vendor/phpunit/phpunit.php processes user-controlled parameters that directly affect file access operations without adequate validation, sanitization, or path restriction. This allows a remote attacker to exploit Path Traversal techniques to read arbitrary files from the underlying operating system and application directories, leading to sensitive information disclosure.