If you're using IE11 and Windows 8 or 8.1, the problem is most likely on Faceboook, but you can get around it by switching to Compatibility View. http://windows.microsoft.com/en-us/internet-explorer/use-compatibility-view#ie=ie-11
Have you automatic updates activated for Flash Player?
If yes, then you got the update notification from that.
If not, then the message may have been a fake.