Hello
The latest versions of CKFinder (2.3) and FCKEditor(2.6.8) are accepting SWF as a valid extension. As a result, it is possible to make a website vulnerable to an XSS attack by uploading a malicious SWF file.
Source: http://soroush.secproject.com/blog/2012/11/xss-by-uploadingincluding-a-swf-file/

This has been reported to the vendor today, but the swf file is public currently via my blog.

PoC: 
Demo Link: http://ckfinder.com/demo
Result: http://ckfinder.com/userfiles/flash/Public%20Folder/XSSProject.swf?js=alert(document.domain)


Regards
Soroush Dalili