How an attacker circumvented crossdomain.xml

Question

I am not sure if I understood the use of crossdomain.xml . I am using Uploadify (2.1.4), a flash file downloader. I need to upload files from Domain A to Domain B Uploadify is hosted and hosted with Domain A To allow the Uploadify Flash plugin to communicate and load in Domain B , I have to place the crossdomain.xml file on Domain B Thus, if Uploaded finds the crossdomain.xml file on Domain B , which has Domain A in the white list, then the file will be downloaded to Domain B Everything sounds so far.

However, I don’t understand what prevents the attacker from creating a bootloader clone on the local website on his computer and subsequently modifying etc/hosts so that the local installation uses Domain A as the domain name. Now, an attacker can upload files to Domain B , pretending that he Domain A and Domain B will openly accept the download, since it has Domain A listed in the white list in crossdomain.xml .

What is the purpose of crossdomain.xml if it can be easily circumvented as above? I could be completely wrong in my understanding of this. It would be helpful to understand.

Answer 1

crossdomain.xml cannot replace the login system. He simply says Flash: "Hey, you can read (and use) data from my server."

crossdomain.xml is really easy to get around, so it cannot be considered as a proper security feature for a website.

So, to summarize, if you want to be safe, just use the login function of your "DomainB".