CVE-2026-41591

Description

Marko is a declarative, HTML-based language for building web apps. Prior to marko version 5.38.36 and prior to @marko/runtime-tags 6.0.164, when dynamic text is interpolated into a <script> or <style> tag the Marko runtime failed to prevent tag breakout when the closing tag used non-lowercase casing. An attacker able to place input inside a <script> or <style> block could break out of the tag with </SCRIPT>, </Style>, etc. and inject arbitrary HTML/JavaScript, resulting in cross-site scripting. This issue has been patched in marko version 5.38.36 and @marko/runtime-tags 6.0.164.

Weakness classification

• CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Primary references

• security-advisories@github.com — Exploit, Mitigation, Patch, Vendor Advisory
• 134c704f-9b21-4f2e-91b3-4a467353bcc0 — Exploit, Mitigation, Patch, Vendor Advisory