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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:L

EPSS

• CVE-2026-41886: 0.10% estimated exploitation activity in the next 30 days; percentile 0.90 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Versions of the locize client SDK (the browser module that wires up the locize InContext translation editor) prior to 4.0.21 register 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. Impact Depending on which handler the attacker invokes, distinct consequences follow. All of them share the same root cause: the handlers implicitly assumed the payload came from the real editor iframe. -…

Published by the source

22 Apr 2026, 20:32 UTC

Last modified by the source

13 May 2026, 13:54 UTC

Source last checked

26 Oct 2026, 12:52 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w937-fg2h-xhq2

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w937-fg2h-xhq2

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# Patch Next advisory brief: CVE-2026-41886

Advisory: locize Client SDK: Cross-origin DOM XSS & Handler Hijack Through Missing e.origin Validation in InContext Editor
IDs: CVE-2026-41886, GHSA-w937-fg2h-xhq2
Record: https://patchnext.com/advisories/cve-2026-41886 (revision 2, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: locize 4.0.21. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm locize: affected < 4.0.21; fixed in 4.0.21

## Suggested inspection (read-only)
- `npm ls locize --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on locize.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-w937-fg2h-xhq2 (OSV record GHSA-w937-fg2h-xhq2 lists affected ranges: npm locize >=0 <4.0.21 (fixed))
- Verified: https://github.com/advisories/GHSA-w937-fg2h-xhq2 (GitHub-reviewed advisory GHSA-w937-fg2h-xhq2 lists affected ranges: npm locize >=0 <4.0.21)

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