xwiki-platform-administration-ui vulnerable to privilege escalation

XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. Any user with edit rights on a page (e.g., it's own user page), can execute arbitrary Groovy, Python or Velocity code in XWiki leading to full access to the XWiki installation. The root cause is improper escaping of the section ids in `XWiki.AdminFieldsDisplaySheet`. This page is installed by default. The vulnerability has been patched in XWiki versions 15.0-rc-1, 14.10.1, 14.4.8, and 13.10.11.