This attack allowed for a cross store (so essentially unauthenticated, 
as we have not authenticated to our target store) privilege escalation 
attack creating an administrative user on any *.gostorego.com store.

As indicated by their own website, there are over 200,000 active 
stores.  This attack allows access to 200,000 x Customers x data = Y.  
Due to the nature of the attack, it would trivial to automate an attack 
that would give us an administrative account on each of these stores 
with a single GET request !!  Or you could simply have a great shopping 
experience.  Google search site:gostorego.com, find the items you want 
to purchase.  Create you admin account (or use stealth mode so all 
attacks are logged as the Store Owner), change the price then buy it or 
simply give yourself some store credit.

This vulnerability was reported to the eBay Enterprise Bug Bounty team 
on Sunday 9th February 2014.

They and the Magento engineering team put out a fix for this issue 
extremely quickly.  So pats on the back all around are deserved.  I 
tested the issue and tried a few work arounds, but the fix holds good.  
So I want to say a big thanks to them.

Full issue with screen shots can be found at http://www.securatary.com 
within the vulnerabilities section.

All the best

Mark Litchfield
www.securatary.com