Should the parent window be able to navigate the popup window, even if it&#x27;s cross origin?<p>If not, now you&#x27;re suggesting some sort of asymmetric security checks that depend on something that&#x27;s not just the origins.  Security checks that, chances are, will be easy to evade by malicious actors.  At least I haven&#x27;t thought of a non-evadable one here yet.