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High, CVSS 8.3amended

CleverTap Web SDK is vulnerable to DOM-based Cross-Site Scripting (XSS) via window.postMessage

CVE-2026-26862GHSA-jfrq-hj9f-c8qx

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (clevertap-web-sdk 1.15.3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L
EPSS
  • CVE-2026-26862: 0.42% estimated exploitation activity in the next 30 days; percentile 36.61 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

CleverTap Web SDK version 1.15.2 and earlier is vulnerable to DOM-based Cross-Site Scripting (XSS) via window.postMessage in the Visual Builder module. The origin validation in src/modules/visualBuilder/pageBuilder.js (lines 56-60) uses the includes() method to verify the originUrl contains "dashboard.clevertap.com", which can be bypassed by an attacker using a crafted subdomain.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-jfrq-hj9f-c8qx

  2. Revision 1 · created ·

    Published from osv record GHSA-jfrq-hj9f-c8qx

Agent brief

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# Patch Next advisory brief: CVE-2026-26862

Advisory: CleverTap Web SDK is vulnerable to DOM-based Cross-Site Scripting (XSS) via window.postMessage
IDs: CVE-2026-26862, GHSA-jfrq-hj9f-c8qx
Record: https://patchnext.com/advisories/cve-2026-26862 (revision 2, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: clevertap-web-sdk 1.15.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm clevertap-web-sdk: affected < 1.15.3; fixed in 1.15.3

## Suggested inspection (read-only)
- `npm ls clevertap-web-sdk --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on clevertap-web-sdk.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-jfrq-hj9f-c8qx (OSV record GHSA-jfrq-hj9f-c8qx lists affected ranges: npm clevertap-web-sdk >=0 <1.15.3 (fixed))
- Verified: https://github.com/advisories/GHSA-jfrq-hj9f-c8qx (GitHub-reviewed advisory GHSA-jfrq-hj9f-c8qx lists affected ranges: npm clevertap-web-sdk >=0 <1.15.3)

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