I am planning to keep this post short and sweet. So, here is the deal. Meta Files are dangerous. Today I am going to cover some of my Security findings that concern files with extensions .wax, .wvx, .asx and .wmx.
Before we continue with the fun stuff, you must understand the purpose of the file formats listed above. First of all, they are meta files just like Apple’s QTL. Second, they are standard for the Windows operating system and supported by default. Finally, the meta files are often used to stack together various media content into playlists.
if you start researching the Media Player meta files (this is a good resource to start), you will see that they all have the same structure, which is XML. The XML document (starting with root node <ASX>) provides the basic characteristics of how the media streams need to be played, what sequence they follow and how the user can interact with them. Digging deeper into the XML, I found several tags which can be abused for malicious purposes. I am going to cover only one of them since the post has to be short as I said earlier.
More: http://www.gnucitizen.org/blog/backdooring-Windows-media-files