CVE-2026-59729 Astro: XSS via unescaped spread attribute names in renderHTMLElement (incomplete fix for CVE-2026-54298)

Astro is a web framework for content-driven websites. Versions prior to 7.0.6 are vulnerable to XSS through unescaped spread attribute names in renderHTMLElement. The fix for CVE-2026-54298 GHSA-jrpj-wcv7-9fh9 added an INVALIDATTRNAMECHAR guard to addAttribute so that spread-prop attribute names...