Shell extensions are other people's code in DLLs which are automatically loaded into other programs (such as Opus) when they do certain things, and then that code (e.g. written by Google in this case) runs inside those programs (e.g. dopus.exe). That code can do anything, including crashing the process or causing other problems. It's entirely outside out control, other than that we have the ability to block some DLLs being loaded in some situations. (We do that for a few which have had problems reported consistently for a long time without updates/fixes from the vendors, but it's rare for it to be needed.)