GHSA-H5JC-78HR-3PC9 Sveltia CMS: Stored XSS in Markdown/RichText preview via unsandboxed same-origin iframe

Impact A stored cross-site scripting XSS vulnerability affected the Markdown/RichText field preview renderer in Sveltia CMS. The DOMPurify sanitization configuration used for Markdown previews explicitly permitted iframe elements without enforcing a sandbox attribute or restricting iframe sources...