Improvements made to version 7.6.7600.256 of the Windows Update Agent
• Hardened Windows Update infrastructure so that the Windows Update client will only trust files signed by a new certificate that is used solely to protect updates to the Windows Update client.
• Strengthened the communication channel used by Windows Update Client to protect it in a similar way.
Paragraph from this LINK rdave13 it appears it isn't being offered to everyone at once - WU Agent v7.6.7600.256 is being rolled-out over time to avoid overwhelming the update servers. Until it's offered to your computer, 7.4.7600.226 is perfectly safe assuming KB2718704 & all other updates are installed and your anti-virus application is installed & working properly.
This look like one of those updates that will install regardless of your settings for security reasons. As for that net\framework I don't have it on my PC. Not in Microsoft update list and not showing after a search.