How to Allow Window.opener.location.href Permission For Greasemonkey?

Question

I'm using GreaseMonkey in FireFox with the following code

if (window.opener) 
{
    alert(window.opener.location.href);
}

However, i'm getting a Permission Denied error, possibly due to cross-domain policy. How do i overcome this protection?

Answer 1

You can't do this if the window is on a different domain than its opener. For plain javascript, blocking this information is considered a security safeguard.

For Greasemonkey, it might be less of a security problem, but the Greasemonkey devs have not added that capability. Greasemonkey is just plain javascript, with select, limited, extension capabilities added on.

You can open a feature request for for this, but it is unlikely to be approved unless you can make a good case for both: how this is useful, AND how it won't result in careless GM users being "pwned".

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In the meanwhile, you can always fork the Greasemonkey source code and build your own version that breaks the cross-domain barrier.

Or, depending on what you are really trying to do, there may be a workaround involving two or more script instances communicating. Open a new question and describe the scenario, in full detail, for help with a workaround.