Input validation vulnerability in Product page shipping calculator for WooCommerce 1.3.20

The Product page shipping calculator plugin for WordPress (WooCommerce) has a security vulnerability that could allow a person with administrator-level access to inject malicious code into web pages. This code would then be executed whenever someone visits the page. This only affects websites with multiple sites and websites where a certain type of code has been disabled. Versions of the plugin up to and including 1.3.20 are vulnerable.