LS simple guestbook - arbitrary code execution

[jd2k2000@hotmail.com]

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#   Special Greetings To - Timq,Warpboy,The-Maggot     #
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File: index.php
Affects: LS simple guestbook (v1)
Date: 15th April 2007

Issue Description:
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LS simple guestbook fails to sanitize user input that it writes to the 
posts.txt file when the user leaves a message, this file is then included 
causing any php code within it to be run.
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Scope:
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An attacker can inject arbitrary php code and potentially execute commands 
on the system.
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Recommendation:
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Add the following line of code in index.php: 

$message = strip_tags($message);

just above: 

if ($message != "") {$file = fopen("$dataf","a");
===========================================================================


Example:

name = Test
message = <?php phpinfo(); ?>


Discovered By: Gammarays