Xbox Live "Core Services" Are Down (Don't Blame Titanfall)

Of all the times for Xbox Live to be experiencing "limited service".

Microsoft's Xbox Live has been having some pretty serious issues for the past hour or so.

I could sign into my account (both in a browser and on my Xbox One), but couldn't sign into Titanfall or access stores. Your mileage may vary; others can access the stores, but are having trouble signing in in the first place.

Right now Microsoft's Xbox Live service page is saying that "core services" are "limited".