Just got a new Android 4.3 update (JWR66Y)

My Nexus 10 just got a new 4.3 update today. It's a 1.8 mb download that doesn't change the version number (still 4.3), although it changes the build number (JWR66Y from JWR66V). Did anyone else get the update? My Gnexus hasn't got anything yet. I wonder what the differences are (if any), maybe a security issue?