The code that provides a direct upgrade path from very old, unsupported Crowd (< 2.0, released in July 2009) versions to the latest version makes direct use of now-unsupported classes and methods in Hibernate. If this code prevents an upgrade to Hibernate 4 then the cleanest option may be to remove it.

Customers upgrading from an earlier version would need to first install Crowd 2.[0-6] before upgrading to a later version.