KLA10543
Security bypass vulnerability in Microsoft Silverlight

An unspecified vulnerability was found in Microsoft Silverlight. By exploiting this vulnerability malicious users can bypass security restrictions. This vulnerability can be exploited remotely via an unknown vectors.

Microsoft Silverlight 5 versions earier than 5.1.30214.0
Silverlight 5 Developer Runtime versions earlier than 5.1.30214.0

Install necessary updates from the KB section, that are listed in your Windows Update (Windows Update usually can be accessed from the Control Panel)