Loading SWF (which itself loads external data) from a different domain

Hello, AS3-beginner here.

I have an .swf (X) which I don’t have the original .fla-file for, as it has been generated by a custom generator. Hence, I cannot modify X.swf in any way and have to use it as it is. X.swf loads several external files, namely XML and images. X.swf and its data are situated on our company server.

As X.swf is to be used as a banner for a client on a different website, and since banners need to be delivered as single .swf-files, I have created a container (Y) that in theory should load X.swf from our company server.

When both X.swf and Y.swf are on the same server and loading from the same domain, it works. When Y.swf tries to load X.swf from a different domain, though, it doesn’t. I have already generated a crossdomain.xml which should grant Y.swf access to X.swf.

Is what I am trying here even possible without the means to modify X.swf (I only have the .swf, not the .fla)?