. Because these files are modified by third parties, they can carry significant risks: Security Risks:

When the file finally opened, there was no player interface. His screens went black, then blossomed into a terrifyingly sharp resolution. It wasn't a video; it was a live-rendered environment. He was standing in a cold, concrete hallway. The textures were so high-definition he could see the microscopic pores in the cement and the way the emergency lights refracted through the dust motes.