GHSA-j5mf-6rh3-rhgg

CleverTap Web SDK is vulnerable to DOM-based XSS via handleCustomHtmlPreviewPostMessageEvent function

Source: GitHub Advisory Database (reviewed) High CVE-2026-26861

Packages

Ecosystem	Package	Affected	Fixed in
npm	clevertap-web-sdk	< 1.15.3	1.15.3

Details

As written in the advisory (Markdown source, shown as plain text).

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.

References

External links from the advisory. They lead to third-party sites.

https://nvd.nist.gov/vuln/detail/CVE-2026-26861 advisory
https://github.com/CleverTap/clevertap-web-sdk/issues/424 web
https://github.com/CleverTap/clevertap-web-sdk/pull/417 web
https://github.com/CleverTap/clevertap-web-sdk/commit/84695b726a751614ddc3a4f71382c239c5833e03 web
https://github.com/CleverTap/clevertap-web-sdk package
https://github.com/CleverTap/clevertap-web-sdk/blob/cf1b65d/src/util/campaignRender/nativeDisplay.js#L118-L121 web