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 doesnt 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.
The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.
It is often convenient to serialize objects for communication or to save them for later use. However, deserialized data or code can often be modified without using the provided accessor functions if it does not use cryptography to protect itself. Furthermore, any cryptography would still be client-side security – which is a dangerous security assumption. Data that is untrusted can not be trusted to be well-formed. When developers place no restrictions on “gadget chains,” or series of instances and method invocations that can self-execute during the deserialization process (i.e., before the object is returned to the caller), it is sometimes possible for attackers to leverage them to perform unauthorized actions, like generating a shell.