Shopify: Preview bar: Incomplete message origin validation results in XSS

The JavaScript code at https://cdn.shopify.com/s/assets/storefront/bars/previewbarinjector-73a4756a265c637c998799750759ae548e7f68b136e8e93e83132904afc3d30d.js loaded by the shop front when a theme is previewed installs a message event listener. The following check is used to reject invalid event...