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

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Summary

CVECVE-2026-41886
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-08 16:16:12 UTC
Updated2026-05-08 16:16:12 UTC
Descriptionlocize 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

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

EPSS: 0.000150000 probability, percentile 0.032660000 (date 2026-05-12)

Problem Types: CWE-79 | CWE-346 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | CWE-346 CWE-346: Origin Validation Error

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:L
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
High
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Locize Locize affected < 4.0.21 Not specified

References

ReferenceSourceLinkTags
github.com/locize/locize/security/advisories/GHSA-w937-fg2h-xhq2 [email protected] github.com
github.com/locize/locize/releases/tag/v4.0.21 [email protected] github.com
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