Since today, the usual 2FA verification dialog that pops up when accessing a collaborator store isn’t showing the Verify button. In Firefox, I can scroll the button iframe’s viewport and see that it’s not loading because accounts.shopify.com is preventing it from loading inside an iframe (the dialog is being served from admin.shopify.com.
Here’s a screenshot from Chrome:
I can open the iframe in a new tab, which then renders the Verify button and I can complete the verification that way, but this looks like a bug in accounts.shopify.com’s Content-Security-Policy or X-Frame-Options header.