Cross-origin DOM XSS via unvalidated postMessage origin
Published May 8, 2026 · Updated May 8, 2026
Cross-origin DOM XSS in the Locize client SDK before 4.0.21 allows remote attackers to execute JavaScript via crafted postMessage events. The message listener in src/api/postMessage.js trusts an attacker-controlled sender field instead of validating event.origin, then routes payloads to handlers that write innerHTML and dangerous attributes. Exploitation requires an attacker-controlled page to share a window reference with the locize-enabled host through an iframe, opener, or parent relationship.
Summary
What happened
Cross-origin DOM XSS in the Locize client SDK before 4.0.21 allows remote attackers to execute JavaScript via crafted postMessage events. The message listener in src/api/postMessage.js trusts an attacker-controlled sender field instead of validating event.origin, then routes payloads to handlers that write innerHTML and dangerous attributes. Exploitation requires an attacker-controlled page to share a window reference with the locize-enabled host through an iframe, opener, or parent relationship.
The record
- CVE
- CVE-2026-41886
- Published
- May 8, 2026
- Updated
- May 8, 2026
- Vendor
- Locize
- Product
- locize
- Classifications
- CWE-79, CWE-346, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 8, 2026CVE publishedPublication date reported by the CVE source.
- May 8, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 4.0.21
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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