Created attachment 478848 [details] testcase Windowless only, mouse input seems to be delivered randomly. pretty easy to reproduce on www.silverlight.net's showcase.
ipc-disabled isn't the default or recommended configuration, so I'm not sure why we'd block on this.
When you DISABLE the Plugin-Container.exe and simply want USE this Widget: http://widgets.freestockcharts.com/CustomizeInteractive.aspx?guid=2d4e7b25-088a-4813-839a-35e2ececaeae&w=300&h=300 You CAN'T use the mouse to control the Silverlight apple, it is needed for using the chart. But with the Plugin-Container.exe ENABLED all work fine with the Silverlight applet and using the mouse to drive... I found this "bug" cause I have a machine running on LOW memory, so disabling the container giving me the memory I need to run FF with the Silverlight applet and others softwares at the same time. NB: On the main page of FreeStockCharts (Who is basically the same as the widget) it work fine with or without the Plugin-Container.exe http://www.freestockcharts.com/ It has been since FF 4.x at least. Regards
I'm marking this bug as WONTFIX per bug #1269807. For more information see - https://blog.mozilla.org/futurereleases/2015/10/08/npapi-plugins-in-firefox/