响应。ContentType盾应用程序/。ms excel xls停止工作

I've done some pretty deep searching on this issue with no luck. It seems that in the past couple of days the output to XLS from HTML has stopped working on many legacy (read: Classic ASP) systems I support. I've been able reproduce this on multiple servers, multiple independent source code from Office 2010 through Office 2016. I've looked at everything I can think of without success so I'm curious to know if there is something I might be overlooking. I'm starting to think this may be a bad Office update that is the culprit.I've done some pretty deep searching on this is