MediaWiki before 1.19.24 1.2x before 1.23.9 and 1.24.x before 1.24.2 when using HHVM allows remote attackers to cause a denial of service (CPU and memory consumption) via a large number of nested entity references in an (1) SVG file or (2) XMP metadata in a PDF file aka a \billion laughs attack \ a different vulnerability than CVE-2015-2937.