NIST deprecates RSA-2048 from 2030. Find every one of them before attackers do.
📦
📦 npm
Not in CISA KEV
HIGH severity

CVE-2026-26861 — clevertap-web-sdk

HIGHFix: CleverTap/clevertap-web-sdk#417

CVE-2026-26861 is a high-severity (CVSS 8.3) CWE-346 vulnerability in clevertap-web-sdk. A fix is available for clevertap-web-sdk — see the affected versions and patch details below.

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

Also known asGHSA-j5mf-6rh3-rhgg
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 1, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-26861.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk-0.02%
Lower risk than most CVEs11th percentile — riskier than 11% of all scored CVEsHighest risk
0.00%0.24%0.48%0.72%0.0%0.2%May 26Aug 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

12other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
clevertap-web-sdknpm
42Kdownloads / week

Description

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 Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmclevertap-web-sdkall versions1.15.3npm install clevertap-web-sdk@1.15.3

Affected Products

1 product · 1 configurations
Application
clevertap web sdkclevertap
≤ 1.15.2
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for clevertap-web-sdk, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update clevertap-web-sdk to 1.15.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-26861 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

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
O3 Security · Impact-Aware SCA

Is CVE-2026-26861 in your dependencies?

Find it across npm, including transitive dependencies.

Scan my dependencies How O3 SCA works
CVE-2026-26861: clevertap-web-sdk XSS — Fixed in 1.15.3