CVE-2026-40262: Note Mark has Stored XSS via Unrestricted Asset Upload

A stored same-origin XSS vulnerability allows any authenticated user to upload an HTML, SVG, or XHTML file as a note asset and have it executed in a victim’s browser under the application’s origin. Because the application serves these files inline without a safe content type and without nosniff, browsers can sniff and render active content, giving the attacker access to authenticated Note Mark API actions as the victim.