We currently use the UnsupportedClassConverter method in UtilXml class. When the 1.5 version of XStream will be available another way to handle this kind of things will be available and used by default. It's already possible to use the same with the 1.4 version of XStream with its setupDefaultSecurity method.
So this Jira to replace the UnsupportedClassConverter in UtilXml class by XStream::setupDefaultSecurity method.
It's an improvement but better to backport it as much as possible