XWiki Platform vulnerable to reflected cross-site scripting via xredirect parameter in delete template

XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. Users are able to forge an URL with a payload allowing to inject Javascript in the page (XSS). It's possible to exploit the delete template to perform a XSS, e.g. by using URL such as: > xwiki/bin/get/FlamingoThemes/Cerulean?xpage=xpart&vm=delete.vm&xredirect=javascript:alert(document.domain). This vulnerability exists since XWiki 6.0-rc-1. The vulnerability has been patched in XWiki 14.10.6 and 15.1. Note that a partial patch has been provided in 14.10.5 but wasn't enough to entirely fix the vulnerability.