Apologies if this has already been stated before, I tried looking through and only found people stating that iframes could not be pasted into, which is not what this post is about.
I was on https://www.humblebundle.com updating my account information (linking 1Password OTP to the account) and also linking in 3rd party accounts. Steam, Twitch, and Battle.net all opened their OAuth pages in a separate tab, which 1Password was obviously able to work with perfectly.
However when I tried to link the Origin/EA account it opened the OAuth page in an iframe. When I had 1Password autofill it was able to paste the username/password into the login form, but it pasted the credentials for Humble Bundle, not Origin.
It seems that it is reading the url of the browser window, not the iframe window?
1Password Version: 7.2.2
Extension Version: 7.2.2
OS Version: macOS 10.14.2
Sync Type: My 1Password