Improper Encoding or Escaping of Output Affecting astro package, versions <7.0.4
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-ASTRO-18085579
- published21 Jul 2026
- disclosed20 Jul 2026
- creditJared Gore
Introduced: 20 Jul 2026
NewCVE-2026-59727 (opens in a new tab)How to fix?
Upgrade astro to version 7.0.4 or higher.
Overview
astro is an Astro is a modern site builder with web best practices, performance, and DX front-of-mind.
Affected versions of this package are vulnerable to Improper Encoding or Escaping of Output via the transition:persist, transition:scope, or transition:persist-props directives when unescaped values are copied onto the rendered <astro-island> element. An attacker can inject arbitrary HTML or JavaScript into the server-rendered output by supplying crafted input that is reflected into these directives.
Note: This is only exploitable if the application developer passes untrusted, request-derived input directly into a transition directive.
Workaround
This vulnerability can be mitigated by ensuring that untrusted or request-derived input is not passed into transition:persist, transition:scope, or transition:persist-props, or by HTML-escaping or strictly validating such input before use.