locize Client SDK: Cross-origin DOM XSS & Handler Hijack Through Missing e.origin Validation in InContext Editor
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- High
- Impact type
- Security bypass, Cross-site scripting
- Confidentiality · integrity · availability
- Low · High · Low
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-346 and CWE-79.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| locize | locize | before 4.0.21 | 4.0.21 | Patch available | CNA |
| — | locize (npm) | before 4.0.21 | 4.0.21 | Patch available | GHSA-w937-fg2h-xhq2 |
- locize Vendorlocize Affected before 4.0.21 Fixed in 4.0.21 Patch available CNA
- locize (npm) Vendor— Affected before 4.0.21 Fixed in 4.0.21 Patch available GHSA-w937-fg2h-xhq2
Remediation
- Fix · CNA locize (locize) Fixed in 4.0.21
- Fix · GHSA-w937-fg2h-xhq2 locize (npm) Fixed in 4.0.21 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-41886
- 2026-10-03 Alias added: GHSA-w937-fg2h-xhq2
References
Other 5
- https://github.com/locize/locize/security/advisories/GHSA-w937-fg2h-xhq2
- https://github.com/locize/locize/releases/tag/v4.0.21
- https://github.com/locize/locize/commit/d006b75fadb8e8ab77b023e462850fc6e9170735
- https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage#security_concerns
- https://github.com/locize/locize
More locize vulnerabilities
- TI-2026-40016 gettext-converter: Prototype pollution in js2i18next() via crafted translation keys CVSS 4.0HIGH 8.3
- TI-2026-30288 Path traversal / URL injection via unsanitised lng/ns/projectId/version in i18next-locize-backend CVSS 3.1MEDIUM 6.5
Sources
- CVE-2026-41886 · CVE Program
- CVE-2026-41886 · NVD
- FIRST EPSS
- GHSA-w937-fg2h-xhq2 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences