Delete button does not ask for confirmation if you are deleting an asset that is not being edited at the time.
If you are editing an asset and delete the same asset the dialogue box says something like "you are about to delete the asset you are editing currently, are you sure", but if you try to delete another asset while you are still editing another asset (This is possible because you are able to borrows the files on the left of the editor window), it just deletes the asset without asking any confirmation. This is not good since users can delete some files by accident and there is no way to recover them from the editor at the moment (there is no undo).