Flexible Subscriptions < 1.8.2 - Authenticated (Customer+) PHP Object Injection

Description

The Flexible Subscriptions plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 1.8.1. This is due to deserialization of untrusted input. This makes it possible for authenticated attackers, with customer-level access and above, to inject a PHP Object. No known POP chain is present in the vulnerable software. If a POP chain is present via an additional plugin or theme installed on the target system, it could allow the attacker to delete arbitrary files, retrieve sensitive data, or execute code.