This host is missing an important security update according to Microsoft Bulletin MS13-087.
Successful exploitation will allow remote attackers to obtain potentially sensitive information. Impact Level: Application
Download and update mentioned hotfixes in the advisory from the below link, https://technet.microsoft.com/en-us/security/bulletin/ms13-087
Flaw is caused when Silverlight improperly handles certain objects in memory.
Microsoft Silverlight version 5 on Mac OS X
Get the installed version with the help of detect NVT and check the version is vulnerable or not.