Silverlight: the next plugin Apple will be blocking

Shhh… Silverlight’s been updated for Mac

So by shear accident, I was in Windows 7 via Boot Camp today. I decided to run updates and actually look at what was being updated. I noticed there was a new Silverlight update, 5.1.20125.0, speak of the devil, in my XProtect Plugin Checker post, not long ago, I speculate when Silverlight will be blocked by Apple because of a security update. Security bulletin MS13-022 explains the critical nature of this for Windows and Mac, if you want to see an MS engineer tell you it’s Priority 1 this month you can visit the Microsoft March 2013 security update page. You’ll need Silverlight to watch the video, but don’t worry it won’t give you prompt you to update. Neither does Netflix. Apparently Microsoft haven’t pulled the trigger to alert users with old Silverlight plugins! Are they waiting for this 14.9MB package to replicate around the world to all the Akamai distribution servers or something? I think it’s done now.

Whither Thou Goest Check for Updates (or Preferences for that matter)?

So I decided to double check my auto-update settings in Silverlight. Would you like to check your Silverlight Preferences? The easy way is to Control-Click/Right-Click on Silverlight content and select About Silverlight from the menu. But take a real world example: you are at a site that won’t load it’s Silverlight content because the caches need cleaning! (This really happened to someone I had to support remotely via email).

Let’s go spelunking!
Opening Silverlight Preferences the hard way:

Navigate to /Library/Internet Plug-Ins
Control-Click on Silverlight.plugin and Show Package Contents
Navigate into Contents/Resources
Double click Silverlight

Or type this in at Terminal:

open /Library/Internet\ Plug-Ins/Silverlight.plugin/Contents/Resources/Silverlight\

I ended up making a .command file to do this, zipped it up, and emailed it so the user could simply empty the Silverlight caches and get back to work (if this was for real work or Netflix I’m not sure…) but regardless, a Preference Pane would be kinda nice MS Silverlight dev folks! All it has to do, at bare minimum, is open this very same app inside the plugin bundle (so we don’t have to dig for it). That’s what the Oracle Java 7 prefPane does. I digress here’s my settings:


Yep that’s set…
OK so Microsoft doesn’t think this Priority 1 update needs updating yet on the Mac?

For fun, in the same folder you can run to see this:


Clicking Install now launches the URL: which will automatically start downloading the newest version of Silverlight.

Exploring the XProtect Factor

Now, I though to myself, if Microsoft doesn’t start getting people to update, I think I know what Apple’s gonna do… but they haven’t done it yet. So I did. I edited my XProtect.meta.plist and blocked Silverlight myself:


Just wedged it right in there with TextWrangler! Now, what happens when I visit a Silverlight page in Safari?

Blocked @ Netflix

Boom, blocked. Aha! This mechanism is quite extensible to whatever plugin Apple deems insecure. Interestingly though, this warning will appear only once in Safari.

Blocked Small

After that your Silverlight content will simply not load and you won’t be told why. The bundle name and version are set under the PreviouslyAnnouncedBlockedPlugins key in and that’s it. Clicking OK in a hurry without reading the message might leave you scratching your head, while repeatedly clicking reload at Netlflix.

Safari Warning XML

Taking a peek at my XProtectPluginChecker I see it’s able to compare the installed version to the values XProtect.meta.plist has. My script is working dynamically, as planned, yay! (I fixed a couple bugs the first few days after posting so re-download if you were an early bird user)

XProtectPluginChecker-silverlightBlockedSo while you may not be seeing this yet I have a strong feeling you will… and when you do XProtectPluginChecker will let you know.

System Administrator Bonus

Say, Mac SysAdmins, wanna disable Silverlight on all your deployed Macs right now? Why? Maybe you want to turn it off right away and worry about installing the update later? BTW this does not block the plugin in Firefox (they have their own mechanism), Safari only.

sudo /usr/libexec/PlistBuddy -x -c "add dict" /System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/XProtect.meta.plist
sudo /usr/libexec/PlistBuddy -x -c "add string 5.1.20125.0" /System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/XProtect.meta.plist

That’ll get your XProtect.meta.plist PluginBlacklist dictionary looking something like this (version vary between 10.6 and 10.7/10.8 machines):

XProtectXML Viola, your Silverlight don’t work no more. :] Now go update it!



4 thoughts to “Silverlight: the next plugin Apple will be blocking”

  1. I downloaded the silverlight installer and was surprised that it is not a signed installer. I know the contextual menu workaround to open it just fine in Mountain Lion, but it was hard for me to believe that an official release from Microsoft wouldn’t be signed.

    The conspiracist in me imagines that the technology is officially abandoned and wonders if this is a case of engineers still pushing an update to the user.

    In the meantime, I might wait until there is a signed release.

  2. You might be waiting awhile! I could see Silverlight Mac support just being dropped. I think Netflix is about the only reason anyone on a Mac has it installed. Sure MS pushes Silverlight integration with Sharepoint, but I have a feeling Sharepoint sites work best in IE on Windows, and Sharepoint is for the Enterprise anyway and Enterprise loves cheap Windows machines. Netflix needs to get a Mac App Store app out already and drop Silverlight, you know it’s totally possible since they already have an iOS app out, so you gotta wonder what the holdup is… App store is 10.6+ and Silverlight is 10.5.7+ is Netlfix concerned about 10.5 users? Doubtful, so kinda puzzling.

  3. Silverlight is required for DRM under Netflix. No more Netflix on AppleTV & Macs?

  4. That’s the thing: I am certain that Silverlight is not running on Apple TV, nor is it being used in the iOS apps. Apple would in no way go for that! So if Silverlight is not needed to stream video content why no Silverlight free Mac App? Perhaps, Netflix is finding it difficult to protect content on a Mac from being ripped vs. the Apple TV/iOS closed system (unless you count jailbreaking)? For the most part, it’s hard to get on the inside of those devices and use debuggers to find memory locations to find decrypted video, whereas the Mac with it’s wonderful BSD facilities like gdb might allow for such interogation. However Apple has blocked gdb (or at least tried) from being used on aps before for this very reason: iTunes. UPDATE/EDIT: I have a strong feeling that Netflix is using Apple’s HTTP streaming technology, it would make sense since it’d be a high profile realworld test of the technology? Maybe, maybe not I haven’t looked at the Netflix app, perhaps I should, this is interesting from the HTTP Streaming RFC:

  5. If the Playlist file contains the EXT-X-ALLOW-CACHE tag and its value
    is NO, the client MUST NOT cache downloaded media segments after they
    have been played. Otherwise the client MAY cache downloaded media
    segments indefinitely for later replay.”
  6. So that for sure would be a tag Netflix would use… hmmm, not enough time in the day…

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