CleverTap Web SDK is vulnerable to DOM-based XSS via handleCustomHtmlPreviewPostMessageEvent function
CleverTap Web SDK version 1.15.2 and earlier is vulnerable to Cross-site Scripting (XSS) via window.postMessage. The handleCustomHtmlPreviewPostMessageEvent function in src/util/campaignRender/nativeDisplay.js performs insufficient origin validation using the includes() method, which can be bypassed by an attacker using a subdomain.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | clevertap-web-sdk | < 1.15.3 | 1.15.3 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2026-26861
- https://github.com/CleverTap/clevertap-web-sdk/issues/424
- https://github.com/CleverTap/clevertap-web-sdk/pull/417
- https://github.com/CleverTap/clevertap-web-sdk/commit/84695b726a751614ddc3a4f71382c239c5833e03
- https://github.com/CleverTap/clevertap-web-sdk
- https://github.com/CleverTap/clevertap-web-sdk/blob/cf1b65d/src/util/campaignRender/nativeDisplay.js#L118-L121
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L- Weakness (CWE)
CWE-346, CWE-79- Platform
- npm
- Package
clevertap-web-sdk- Disclosed
- 27.02.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-j5mf-6rh3-rhgg - CC BY 4.0
Vulnerability history: clevertap-web-sdk
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 02.2026 02.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
Disclosures per year
- 2026: 2
-
CleverTap Web SDK is vulnerable to DOM-based XSS via handleCustomHtmlPreviewPostMessageEvent function this entry
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