CVE-2026-83613 xmldom: Quadratic-time attribute deduplication

xmldom is a pure JavaScript W3C standard-based XML DOM Level 2 Core DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMHandler.startElement in lib/dom-parser.js inserts every parsed attribute through setAttributeNode...