If a URL using the "file:" protocol is dragged and dropped onto an open tab that is running in a different child process the tab will open a local file…

If a URL using the "file:" protocol is dragged and dropped onto an open tab that is running in a different child process the tab will open a local file corresponding to the dropped URL, contrary to policy. One way to make the target tab open more reliably in a separate process is to open it with the "noopener" keyword. This vulnerability affects Firefox < 60.