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.
An open redirect in the Ninja Forms plugin before 3.3.19.1 for WordPress allows Remote Attackers to redirect a user via the lib/StepProcessing/step-processing.php (aka submissions download page) redirect parameter.
The Ninja Forms plugin before 2.9.42.1 for WordPress allows remote attackers to conduct PHP object injection attacks via crafted serialized values in a POST request.
Multiple cross-site scripting (XSS) vulnerabilities in the Ninja Forms plugin before 2.8.9 for WordPress allow (1) remote attackers to inject arbitrary web script or HTML via the ninja_forms_field_1 parameter in a ninja_forms_ajax_submit action to wp-admin/admin-ajax.php or (2) remote administrators to inject arbitrary web script or HTML via the fields[1] parameter to wp-admin/post.php.