Silverlight is designed to make the update experience as seamless as possible, but its designers also considered security awareness as well as enabling user or enterprise managed overrides.
Silverlight knows to kinds of updates .
1. Security related updates. Silverlight checks for security related updates once every 24 hours. Security related updates patch vulnerabilities, but do not provide new features. The 24 hour check interval minimize your exposure to known vulnerabilities.
2. Feature updates. Silverlight checks for feature updates once every 30 days. Feature updates are releases delivering new capabilities, you know the things that help you build even better Silverlight experiences. For example, Silverlight RC is going to check for the 1.0 release once every 30 days.
The Silverlight control has to be running for those checks to occur -- which means the control has to be playing content (which shouldn't be a big deal since there's going to be a LOT of content). When Silverlight will automatically downloads the new version in the background when an update is available and then runs the installation in silent mode to make the new version available the next time your browser starts. Unfortunately, the restart is necessary to unlock the loaded DLL -- remember the control had to be loaded to check for the upgrade. Silverlight will not prompt you to restart the browser if it downloaded a feature updates though. The new version will just magically be there.
Getting security updates installed quickly is more important , because they help you to reduce exposure to vulnerabilities, Silverlight will prompt your to close and re-open your browser to make sure you're safe and your time of exposure is as short as possible.
In most cases the automatic installation of updates means that users should have the latest Silverlight control installed when they browse to a page with content that requires a recently released Silverlight version. There may be a few cutting edge users that browse to content that requires the latest features before it's time for Silverlight to check for a feature update. In that case, you'll see a nice logo (hopefully) to tell you that Silverlight is downloading a new version for you right now and you'll have to wait until download and in-place upgrade are complete. Then you restart your browser and navigate back to your cutting edge content site.
Now, there are a few exception scenarios where Silverlight's update behavior is different:
· You're running on a Mac … your Mac may be cooler than my Thinkpad, but it will detect that an update is available and, based on your update configuraion, redirect you to a Microsoft site to update your version. Your browser will navigate to the Silverlight download page and ask you to verify and install the new Silverlight version.
· You don't like updates and chose to opt out of update checks in the Silverlight configuration. Your choice. We respect your choice and Silverlight will not automatically download and update to new versions. We do believe it's important that you know about security updates and therefore go ahead and check (once every 24 hours) for available update. Instead of downloading and installing updates in the background, we prompt to ask you if you want to install the upgrade. · You work in an enterprise that prefers to retain full control over the software that's running on your computer. They can fully prevent Silverlight from any checking and prompting, get the updates from WSUS an install as they deem necessary.
You see that there's a wide variety of options from automatically, mostly hidden to fully manual.