Path Traversal and Unrestricted File Upload exists in the Ninja Forms plugin before 3.0.23 for WordPress (when the Uploads add-on is activated). This allows an attacker to traverse the file system to access files and execute code via the includes/fields/upload.php (aka upload/submit page) name and tmp_name parameters.
https://www.onvio.nl/nieuws/ninjaforms-vulnerability
https://wpvulndb.com/vulnerabilities/9272
https://wpscan.com/vulnerability/e5898e0e-db43-4641-b2cd-f6a72cdb8993/