The JDK used to build and run JVM-based apps has been updated to OpenJDK6u27 and OpenJDK7u13. You’ll just need to do a new push on your app to get the update. (Note: apps older than September 1, 2012 may need to add a system.properties file.) See the IcedTea blog for details about patches included in the updates: JDK6u27 updates, JDK7u13 updates. If you want to switch from JDK6 to JDK7, or vice versa, see how to update your app to use a different JDK.