This post might be interesting for those concerned about the state of Oracle's Java SE security.
We have successfully confirmed that a complete Java security sandbox bypass can be still gained under the recent version of Java 7 Update 11  (JRE version 1.7.0_11-b21).
MBeanInstantiator bug (or rather a lack of a fix for it ) turned out to be quite inspirational for us. However, instead of relying on this particular bug, we have decided to dig our own issues. As a result, two new security vulnerabilities (51 and 52) were spotted in a recent version of Java SE 7 code and they were reported to Oracle today  (along with a working Proof of Concept code).
Best Regards Adam Gowdiak
Security Explorations http://www.security-explorations.com "We bring security research to the new level"
References: References:  Oracle Security Alert for CVE-2013-0422
http://www.oracle.com/technetwork/topics/security/alert-cve-2013-0422-1896849.html  Java 7 Update 11 Addresses the Flaw Partly Fixed in October 2012, Experts Say
http://news.softpedia.com/news/Java-7-Update-11-Addresses-the-Flaw-Partly-Fixed-in-October-2012-Experts-Say-320792.shtml  Confirmed: Java only fixed one of the two bugs
http://immunityproducts.blogspot.com.ar/2013/01/confirmed-java-only-fixed-one-of-two.html  SE-2012-01 Vendors status http://www.security-explorations.com/en/SE-2012-01-status.html