The PDF Invoices and Packing Slips For WooCommerce plugin for WordPress is vulnerable to PHP Object Injection in all versions up to, and including, 1.3.7 via deserialization of untrusted input via the order_id parameter. This makes it possible for authenticated attackers, with subscriber-level access and above, to inject a PHP Object. No known 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.