You may want to disable the document preview for attachments on a specific Content Item such as a Document or a Blog Post in your Jive Community. This would prevent the users from seeing a preview of the attachment. They will need to download the attachment and open it with a compatible program (such as Microsoft Excel) to see the contents.
This has been identified as a feature and enhancement request and has been documented internally with issue key JIVESPECS-1485. You can bookmark the Jive Cloud Release Schedule page on the Worx portal to know when the enhancement will be released. If you don't already have access to the Worx portal, you can request a Worx account.
Please note that we are unable to provide any timelines for the releases of the features and enhancement requests.