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.