XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. In affected versions it's possible for a user to write a script in which any velocity content is executed with the right of any other document content author. Since this API require programming right and the user does not have it, the expected result is
$doc.document.authors.contentAuthor (not executed script), unfortunately with the security vulnerability it is possible for the attacker to get
XWiki.superadmin which shows that the title was executed with the right of the unmodified document. This has been patched in XWiki versions 14.10.7 and 15.2RC1. Users are advised to upgrade. There are no known workarounds for this vulnerability.