Firefox 48.0a2 After a download of an "uncommon" file from https://testsafebrowsing.appspot.com/ , safe browsing blocks the access in Firefox's download UI. To access it, the user has to click on a menuitem "Allow download". This is confusing because the user already downloaded the file but implies the user has to download it again. Some users even might try to redownload it from the browser instead of using the menu item because they are aware that the file isn't offered over a static URL (e.g. some file hosting services, websites requiring authentication and automatically logging users out after inactivity like company internal websites).