Silverlight for Mac OS X has been blocked for your protection.

Why was it blocked?
Old versions of the Silverlight plugin for Mac OS X are causing serious stability problems in Firefox. Affected users can visit the official Silverlight page and get the latest version of the Silverlight plugin to correct this problem.
Who is affected?
All Firefox users on Mac OS X who have old versions of the Silverlight plugin.
What does this mean?

Users are strongly encouraged to disable the problematic add-on or plugin, but may choose to continue using it if they accept the risks described.

When Mozilla becomes aware of add-ons, plugins, or other third-party software that seriously compromises Firefox security, stability, or performance and meets certain criteria, the software may be blocked from general use. For more information, please read this support article.