The Drag and Drop Multiple File Upload for Contact Form 7 plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 1.3.8.7 via deserialization of untrusted input from the 'dnduploadcf7upload' function. This makes it possible for attackers to inject a PHP Object through a PHAR file. No known POP chain is present in the vulnerable software, which means this vulnerability has no impact unless another plugin or theme containing a POP chain is installed on the site. If a POP chain is present via an additional plugin or theme installed on the target system, it may allow the attacker to perform actions like delete arbitrary files, retrieve sensitive data, or execute code depending on the POP chain present. This vulnerability may be exploited by unauthenticated attackers when a form is present on the site with the file upload action. The Flamingo plugin must be installed and activated in order to exploit the vulnerability. The vulnerability was partially patched in version 1.3.8.8.