MediaWiki before 1.19.24 1.2x before 1.23.9 and 1.24.x before 1.24.2 when using HHVM or Zend PHP allows remote attackers to cause a denial of service (\quadratic blowup\ and memory consumption) via an XML file containing an entity declaration with long replacement text and many references to this entity a different vulnerability than CVE-2015-2942.