The WordPress group just released a update that was partly issued to resolved a security concern.
There was some updates done as well with some nice new features.
Check out their post here for the full details:
Some sites were already updated that are on our hosting platform. Some of you chose to not
do the auto upgrade I am sure, so please check into upgrading your software accordingly.
If you don’t know what to do then contact support for more information and someone will gladly
help you get that done.