Modal shows dot files

[drhowarddrfine]

For the life of me I can never remember how to fix this. Somehow a setting has changed and when I want to open a file in, say, Firefox or other graphical applications, the modal box shows up with the list of files in that directory including all the dot files. It never did that since the last time I fixed that but I just don't recall how to do it. That is, don't show the dot files.