This version has an acceptance list for file extensions allowed in the Documents and Files module. We introduced this list for security reasons, so that it is not so easy to upload files that can execute code. If you have files with a file extension that cannot execute dangerous code and should be uploaded to the module, please let us know via the forum.
A full list of all new features and bugfixes can be found in our issue tracker!
We recommend you to read our announcements for version 4.0 if you have not done before.
If you are new to Admidio and want to install it on your webpage than the following wikipage could help: Install Admidio
The following wiki pages maybe interesting on an Update: Update Admidio