Build Identifier: https://hg.mozilla.org/mozilla-central/rev/9da51cb4974e03cdd8fa45a34086fe1033abfeaf Mozilla/5.0 (Windows NT 6.1; WOW64; rv:47.0) Gecko/20100101 Firefox/47.0 ID:20160229030448 The problem does not happen when e10s is disabled. Reproducible : always with e10s. Steps To Reproduce: 1. Install "Windows Media Player Firefox Plugin" from [1] [1] http://www.interoperabilitybridges.com/windows-media-player-firefox-plugin-download 2. Open attached video file and play 3. Close Browser Actual Results: firefox.exe and plugin-container.exe process remains forever. No crash reports. Expected Results: These process should disappear immediately

I'm not able to reproduce. both content and plugin plugin-containers shut down for me. This plugin is obsolete as well. The installer places the files in the application directory which we don't support by default. ('plugins.load_appdir_plugins' needs to be set.)

Stack(using crashfirefox.exe) bp-adb7f7cd-6e60-47f6-9f1e-17df92160302

(In reply to Alice0775 White from comment #2) > Stack(using crashfirefox.exe) > bp-adb7f7cd-6e60-47f6-9f1e-17df92160302 The main browser is hung waiting on a window to get destroyed. Usually this means Windows is waiting on something to happen in the plugin process associated with the child window. Could be caused by a shutdown hang in the media player, or maybe there's a deadlock in out content process + plugin ipc taking place.