Simple file to reproduce the bug
maxindextest.xlsx (application/vnd.openxmlformats-officedocument.spreadsheetml.sheet), 26.80 KB, created by Markus Kirsten on 2017-12-05 15:03:41 UTC
Creator: Markus Kirsten
Created: 2017-12-05 15:03:41 UTC
Size: 26.80 KB

Attachment is not viewable in your browser because its MIME type (application/vnd.openxmlformats-officedocument.spreadsheetml.sheet) is not one that your browser is able to display.

Download the attachment.

Actions: View
Attachments on bug 61859: 35587