The good people of FireEye Labs posted on discovery of a IE 10 zero-day being used in watering hole attack on a breached server in the US [1].

FireEye are working with Microsoft, so details are fairly thin. To quote from their first short blog post:

"It’s a brand new zero-day that targets IE 10 users visiting the compromised website–a classic drive-by download attack. Upon successful exploitation, this zero-day attack will download a XOR encoded payload from a remote server, decode and execute it."

Those looking after IE 10 users may want to keep an eye on their proxy logs for the follow on download as a potential indicator. 

UPDATE

FireEye have provided a great deal of detail on the attack in a second blog post, which is well worth a read and gives plenty of the indicators of compromise to run through your logs and filters:

http://www.fireeye.com/blog/uncategorized/2014/02/operation-snowman-deputydog-actor-compromises-us-veterans-of-foreign-wars-website.html

[1] http://www.fireeye.com/blog/technical/cyber-exploits/2014/02/new-ie-zero-day-found-in-watering-hole-attack-2.html

Chris Mohan --- Internet Storm Center Handler on Duty