Input validation vulnerability in WooCommerce Product Enquiry 2.3.4

The WooCommerce Product Enquiry plugin for WordPress is a tool that can be used to ask questions about products. Unfortunately, in versions up to and including 2.3.4, the plugin is not secure and makes it possible for unauthenticated attackers to inject malicious code into the webpage. This would require the attacker to be able to convince somebody to enter the malicious code into the form fields.