User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:62.0) Gecko/20100101 Firefox/62.0 Build ID: 20180920131237 Steps to reproduce: Firefox 62.0.2, macOS 10.14 1) Go to a website with an "attach a file" dialog, i.e. an email service 2) Select "Attach a file" on this webpage 3) From finder window, select a file without an extension. This may hang the finder window, as well as the browser. 4) If it doesn't hang at first, click around a bit more on other files, and click back to the file without extension. Continue doing this until a hang. (this works reliably for me) Actual results: Browser/finder window hung when selecting file without extension Expected results: I should have been able to select file without extension and add it to my email.