The workshop settings form now provides two new fields: Submission attachment allowed file types and Feedback attachment allowed file types . TEST 1: As a teacher, make sure that you can define list of allowed file extensions in these fields. TEST 2: Some extensions (such as *.dia) may have to be registered first at Site administration > Server > File types to make them usable in these fields. There are two levels of protection where the uploaded files are being checked for having allowed file type: TEST 3: The file picker should normally prevent you from uploading a file if its extension does not match one of the allowed ones. TEST 4: If you bypass the filepicker check (e.g. by disabling javascript or by renaming the file only after it had been uploaded), attempting to upload a file with not allowed extension should still be prevented by Workshop custom validation rules.