User Registration <= 2.3.2.1 - PHP Object Injection

The User Registration plugin for WordPress is vulnerable to PHP Object Injection in versions up to, and including, 2.3.2.1 via deserialization of untrusted input in the following functions: ur_get_user_extra_fields, user_registration_form_field. This allows subscriber-level attackers to inject a PHP Object. No POP chain is present in the vulnerable plugin. 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.