Fore quite a few years in the past one could attach a file to the post by going Insert->Image/video/file->Path to file->OK. After recent upgrade the system does not allow inserting files of various kinds, most notably the Excel files (.xls, xlsx) and zip archives: it blocks insertion with a message "The file or URL is not allowed to be inserted."
Is that a new, post-upgrade policy? If so, where one could find a list of file types that are allowed for insertion into the posts? What would be a recommended method for the users to exchange data in lieu of Excel?