Nowhere on that banner does Facebook make it clear that there was recently a severe security issue that may have resulted in the loss of personal user information (Making it much less likely for the user to actually click 'Learn More'). It's misleading to title this with just "An Important Security Update" and make it seem like they've just updated their systems. No mention of the recent compromise until you click 'Learn More'.
https://www.facebook.com/help/2687943754764396?ref=comms
Which is the issue at hand.