CVE-2026-59727 — Astro: Cross-site scripting via unescaped transition:* directive values on hydrated islands

Description (CNA)

Astro is a web framework for content-driven websites. In versions 3.10.0 through 7.0.3, when a transition:persist, transition:scope, or transition:persist-props directive is applied to a client-hydrated (client:*) component, Astro copied the directive value onto the rendered <astro-island> element without HTML-escaping it. If a developer reflects attacker-controlled input into one of these directives, an attacker can break out of the attribute and inject arbitrary HTML/JavaScript into the server-rendered output, resulting in reflected cross-site scripting (XSS). Exploitation requires the application developer to have written a non-idiomatic pattern — passing untrusted, request-derived input directly into a transition directive. Astro applications that do not route untrusted input into these directives are unaffected. This issue has been fixed in version 7.0.4.

Affected (CNA)

Vendor / product	Versions
withastro / astro	affected >= 3.10.0, < 7.0.4

CWE

CWE-79, CWE-83, CWE-116

References

ADP enrichment

CISA-ADP

No English description supplied.

https://github.com/withastro/astro/security/advisories/GHSA-7pw4-f3q4-r2p2