Using CKeditor on my project.
Recently installed fmath plug-in. Followed all instruction and created PHP file that will get image from editor and save in website directory.
The problem is, there was something wrong with fmath editor: when I tried to press “Ok” (it must send generated image to php file and show result image in main CKeditor textarea) nothing happened. I activated webconsole of FF and as you see browser tries to get some crossdomain.xml. I think editor configuration has nothing to do with this problem. fmath editor doesn’t even try to send something to php file (firebug doesn’t show any XHR activity)
Can anyone explain me, what can I do in that case?

It is a security issue: crossdomain.xml contains the security policy for the domain you are trying to access. Resolving this issue is (relatively) easy: Just add a crossdomain.xml at the top level of your web server’s content root.
You can learn all about security policies and the Flash security model in Adobe’s documentation, or download this pdf.