The Cart::getProducts method in system/library/cart.php in OpenCart 1.5.6.4 and earlier allows remote attackers to conduct server-side request forgery (SSRF) attacks or possibly conduct XML External Entity (XXE) attacks and execute arbitrary code via a crafted serialized PHP object, related to the quantity parameter in an update request.
karmainsecurity.com/KIS-2014-08
packetstormsecurity.com/files/127460/OpenCart-1.5.6.4-PHP-Object-Injection.html
seclists.org/fulldisclosure/2014/Jul/67
www.securityfocus.com/archive/1/532763/100/0/threaded
www.securityfocus.com/bid/68529
github.com/opencart-ce/opencart-ce/commit/c2aafc823bd85876f5e888f8ebc421069a5e076f