Full details can be found here : https://github.com/rackerlabs/attributeMapping/issues/38
This feature will add more blacklisted functions in the path so that they cannot be accessed from external resources. Specifically, Saxon is not blocking unparsed-text and unparsed-text-available. It has to do with XPath 2.0 features and which functions are allowed in the path.
- block access to unparsed-text, unparsed-tet-available