$ file windows/Downloads/excelreport.xls
windows/Downloads/excelreport.xls: HTML document, Little-endian UTF-16 Unicode text, with CRLF, CR line terminators
Anywhere in Enterprise Manager where Enterprise Manager offers the Excel icon button with "Export" label. It downloads a file called "excelreport.XLS" but the format is not XLS.
Based on the results of my findings the format that pretends to be .xls appears to be html. Checking want's wrong with it with RnD folks, stay tuned.
Update: You can safely modify the extension of the file to html and view that as web page whenever you do not have local Excel installation. Additionally, we've noted an improvement report for next versions.