When you display the order status page (order completion page) directly in the URL on Shopify, you will be asked to verify your identity by email address and order number.

To access Shopify's Order Status Page, you will need to verify your identity by providing your email address and order number (this also applies when opening the page from the admin screen).

New login requirements for the Order Status Page

To enhance the security of merchant and customer information, we've implemented new login requirements to the Order Status Page that leverages advanced security measures to provide additional protection for customer data.

changelog.shopify.com

When you directly access the order status page (order completion page) via URL, you will be asked to verify your identity by entering your email address and order number.