Is It Safe to Download Microsoft Silverlight

Silverlight is Microsoft’s web extension, like Flash or HTML5. It’s completely safe.

Should I install Microsoft Silverlight?

Its not a requirement to have it installed, but as noted, some web pages utilize it for streaming multimedia content. I believe the last Olympics which MSNBC had exclusive rights to stream on the web, required Silverlight. Its what you call a Rich Internet Application, similar to Adobe Flash.

Is Silverlight a security risk?

Once support ends patches and updates will no longer be released by Microsoft. The major risk, of course, is that security vulnerabilities will no longer be addressed and could leave Silverlight based applications open to significant risk of breach.