Redirection for Contact Form 7 <= 3.2.4 - Unauthenticated PHP Object Injection via PHAR Deserialization

Summary

The Redirection for Contact Form 7 plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 3.2.4 via deserialization of untrusted input in the delete_associated_files function. This makes it possible for unauthenticated attackers to inject a PHP Object. This vulnerability may be exploited by unauthenticated attackers when a form is present on the site with a file upload action, and doesn't affect sites with PHP version > 8. This vulnerability also requires the 'Redirection For Contact Form 7 Extension - Create Post' extension to be installed and activated in order to be exploited. 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. We confirmed there is a usable gadget in Contact Form 7 plugin that makes arbitrary file deletion possible when installed with this plugin. Given Contact Form 7 is a requirement of this plugin, it is likely that any site with this plugin and the 'Redirection For Contact Form 7 Extension - Create Post' extension enabled is vulnerable to arbitrary file deletion.