CVE-2026-58263: Jodit Editor: Mutation XSS in jodit clean-html via a MathML/style rawtext carrier

jodit’s built-in clean-html sanitizer can be bypassed by a MathML/<style> carrier that hides a dangerous element from the sanitizer’s element walk, so a no-interaction event handler survives into the editor value. When an application supplies attacker-influenced HTML to the editor’s value-set or insertion paths, the sanitized output still contains a live <img ... onload=...> (or another non-onerror handler such as onfocus). A consumer that renders that output (element.innerHTML = editor.value) executes the handler with no user interaction. This is a stored cross-site scripting vulnerability, confirmed live on the shipped es2021/jodit.min.js for 4.12.25 and the latest 4.12.27 (in Chromium via a client-side innerHTML consumer, and in Firefox via server-rendered / document-context output; see the cross-browser note under Proof of concept).