[Complete] Unscheduled Maintenance - March 23, 2017

I doubt it's entirely about the Choux face

Of course.
As cash-shop-centered as Nexon is, even they won't take the game down for two hours during prime playing time for a cash face. They'd have waited a few more hours 'til everyone in America went to bed.
Obviously there was some kind of major exploit / hack / security breach, that they're too embarrassed to admit to.