we found that you are able to upload a file with a question mark in its name.
Moodle does not show an error when the file is uploaded. But Moodle does not show the file. Also a download of the file is not possible. You are able to change the name and then everything work.
I think that it is a critical error because a lot of users do not know about the problem with question marks in the filename.
Best regards, Ralf