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"/>
Similar to ‘crossdomain.xml’, Silverlight has some security features, this too is often noticeable by large number of HTTP 404 errors for a file named ‘clientaccesspolicy.xml’ in my webserver logs.
The most simple solution to the 404’s that restricts Silverlight is to add an empty file at the root of your websites.
Often it can be beneficial to ‘more’ uniquely identify your users. For applications this is trivial, but in a web browser this can be accomplished via only a few attributes.
- HTTP – User-Agent, IP Address, Content types and languages accepted.
- HTTPS/SSL – the keys and encryption methods available to a specific user may vary for each client configuration.
- HTML5 – local storage and capabilities supported.
- Geolocation – this is included in HTML5, but also supported in many clients without full HTML5 support, or via browser extensions.
- Java (Applet) – Installed version – this can often be used to get additional information regarding the client system directly from the VM or Operating System itself. (* Persistent Cookies possible)
- Flash – Installed version – this can often be used to get additional information regarding the client system directly from the Operating System itself. (* Persistent Cookies possible)
- Silverlight (for Microsoft Windows) – – Installed version and additional information from Operating System?
- GoogleGEARS (deprecated) – Installed version and additional information from Operating System such as Geolocation