'span','div'],
        ALLOWED_ATTR: ['href','src','alt','title','class'],
        ALLOW_DATA_ATTR: false,
        ALLOWED_URI_REGEXP: /^https?:\/\//i
    };
    function initMarkdownSanitizer() {
        if (markdownDomPurifyInitialized || typeof DOMPurify === 'undefined') return;
        // Register hook once: add rel="nofollow" to links, restrict class to code/pre/span/div