This error was showing up related to a WordPress attack from an IP in France. It appears to be trying to exploit JetPack in some way, and it took down my site more than once. My JetPack plug-in was a bit out of date on a couple of my site. Since Evan appears to have figured out that a standard security protection was left out of the Jetpack plugin, I’m hoping this has been corrected in recent releases.
Note: on review of this file in the latest release of JetPack this vulnerability does not have Evan’s code correction, although it does have:
defined( 'ABSPATH' ) or die( 'No direct access, please.' );
which may be playing the same role.