Silverlight was a browser extension that was backed by Microsoft’s .NET product on many platforms, it provided media capabilities similar to Macromedia/Adobe Flash. Similar to Flash, it has had it’s own share of security problems over the years.
Introduced in 2007 and currently in a deprecated state. Once supported on Windows XP (IE6) to Windows 10 (IE11), MacOS and Ubuntu. Now only supported in MSIE. Edge never provided support. Modern versions of Chrome, Firefox, Safari, and Opera no longer support.
HTML Markup example:
<object data="data:application/x-silverlight-2," type="application/x-silverlight-2" width="100%" height="100%"> <param name="source" value="MySilverLightControl.xap"/> </object>
REFERENCES:
https://en.wikipedia.org/wiki/Microsoft_Silverlight