[xwiki-users] Ajax.Query and cross-site AJAX requests?

Hi, I want one of my pages to make a post to another site and insert the results into its page. Right now I've got a JavaScriptExtension that looks like: function doquery() { new Ajax.Request('http://mat.exon.name/test.php', { method:'post', parameters:{ 'arg' : document.getElementById('thearg').value, }, }); return false; } I find that this does an OPTIONS request, but not the intended POST. If I change the URL to a local page, the POST goes through as intended. Am I tripping up over some kind of XSS defense, and is there some way to turn it off?