The vulnerability manifests during HTML paste operations where specially crafted content bypasses sanitization. The PoC demonstrates that Microsoft Word-generated meta tags and <img> onerror handlers are not properly neutralized. This indicates two key points of failure: 1) The paste handling module's HTML processing logic (Paste.prototype.processHTML) that accepts untrusted input, and 2) The core sanitization function (sanitizeHTML) responsible for filtering dangerous elements. Both are explicitly referenced in security advisories as locations where custom sanitization was implemented but found insufficient. The maintainer's acknowledgment of incomplete patching further supports this assessment.