Allowed File Extensions not working

I’ve tried every combination I can think of but I can’t get the Allowed File Extensions to work. For Example:

.jpg, .pdf,
jpg, pdf,
*.jpg*, *.pdf*, (this worked only for the first extension type)
(*.jpg*), (*.pdf*),
(.jpg), (.pdf),
(*.jpg*, *.pdf*,)

Am I doing something wrong or is there a bug in the code?

https://wordpress.org/plugins/wp-file-upload/