Safari in Apple OS X before 10.10 allows remote attackers to cause a denial of service (universal Push Notification outage) via a web site that triggers an uncaught SafariNotificationAgent exception by providing a crafted Push Notification.
Apple Security Advisory 2014-10-16-1 - OS X Yosemite v10.10 is now available and addresses 802.1X, AFP file server, Apache, App Sandbox, and various other vulnerabilities.