December 2014 update for Microsoft Silverlight 5 - Microsoft サポート
This update was released on December 12, 2014 and offers a new build (version 5.1.31211.0) of Microsoft Silverlight for users of recalled version 5.1.31010.0. For more information about Silverlight, go to the What is Silverlight? section.
関連
http://d.hatena.ne.jp/noushibou/20141210/1418166957
追記
動作確認
Windows 8.1 IE 11 / Firefox どちらも OK