[UNIX] phpBB Still Suffers From a Cross Site Scripting Vulnerability (Edit)

From: support@securiteam.com
Date: 03/23/02 

From: support@securiteam.com
To: list@securiteam.com
Date: Sat, 23 Mar 2002 22:24:38 +0100 (CET)

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  phpBB Still Suffers From a Cross Site Scripting Vulnerability (Edit)
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SUMMARY

After a similar bug was discovered in phpBB 1.4.2, the authors fixed the
bug that would allow JavaScript to be inserted by using an [IMG] tag like:
[img]javascript:alert('bla')[/img]

But there was only a check for that only when you posted new messages. If
you just edit an existing message, you still can use the bug to insert
JavaScript.

DETAILS

Vulnerable systems:
phpBB version 1.4.4

There is no check in the edit function of phpBB 1.4.4 whether JavaScript
or other unwanted code is written within IMG-tags.

Exploit:
Create a new topic or answer to an existing one. Then, after posting your
message, click on the "edit button" and enter anywhere in your posting:

[img]javascript:alert(document.cookie)[/img]

After posting the message, you should see the contents of the cookie
matching to the site you are visiting at the moment.

Solution:
Update to newer versions (phpBB2 seems not to be vulnerable) or just
implement a routine which checks if at the beginning of [IMG]-tags stands
a "http://".

ADDITIONAL INFORMATION

The information has been provided by
<mailto:BlueScreen@IT-Checkpoint.net> BlueScreen.

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