Why is Facebook Ads app blocking Chrome extension iframes?

[ncak]

Hi! 

I'm a developer implementing a chrome extension. Some of our users complained that when navigating your Facebook Ads app on https://*.myshopify.com/admin/apps, they are running into errors with modals not opening.

The facebook Ads iFrame is looping through the list of iframes attached to the parent window in order to detect the "app-modal-iframe", but it encounters our iframe first (our extension injects an iframe in the page) and crashes because it is blocked by CORS. As a result, the modal is never opened. 

This is also happening with any other extension that injects an iframe. Wrapping the above code in a "try/catch" should help to mitigate this issue. 

Please let me know if you need more details.