Comment 3 for bug 1608558

List of illegal characters for Windows:

https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx

Linux:

http://www.linfo.org/file_name.html

Mac:

https://support.apple.com/en-us/HT202808

We can't just regex for [\w\d]*, because this would disallow filenames in Arabic, Russian, Chinese etc.