I am talking about attaching files to posts in the forum. In the advanced post editor you can attach files to post (e.g. images or documents). Only certain file types are allowed. It currently says:
My suggestion is for the forum administrators to add "xls" and/or "ods" to that list, so that Excel spreadsheet files (with filenames ending in ".xls") and/or OpenDocument spreadsheet files (with filenames ending ".ods") can be attached directly to posts.
In the same way that "doc" (Microsoft Word documents) is currently allowed.
Currently the way to add them is to zip them first (because zip files are allowed) and attach the zip file to the post.