Privilege escalation from script right to programming right through title displayer

Steps to reproduce:

As a user with script but not programming right, create a document with the following content:

{{velocity}}
#set($main = $xwiki.getDocument('AppWithinMinutes.DynamicMessageTool'))
$main.setTitle('$doc.getDocument().getContentAuthor()')
$main.getPlainTitle()
{{/velocity}}

Expected result:

The string $doc.getDocument().getContentAuthor() is displayed as this call requires programming rights.

Actual result:

XWiki.superadmin or another author with programming rights is displayed.

This shows that a user with script right was able to access an API that requires programming rights because the context document's author is unchanged even though setTitle() has been called. This is because the title displayer sets the original document as context document when executing the modified title.