Vulnerability in Clevertap Web Sdk
CVE-2026-26861
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
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L.
EPSS exploit prediction
EPSS: 0.002 (11.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 12th percentile — 11.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000
Affected products
Weakness classification (CWE)
References
- github.com/CleverTap/clevertap-web-sdk/issues/424 (Exploit, Issue Tracking, Vendor Advisory)
- github.com/CleverTap/clevertap-web-sdk/pull/417 (Patch)
- github.com/CleverTap/clevertap-web-sdk/blob/cf1b65d/src/util/campaignRender/nat… (Product)
Frequently asked questions
- What is CVE-2026-26861?
- CVE-2026-26861 is a high-severity vulnerability in Clevertap Web Sdk, classified under Origin Validation Error. CVSS score: 8.3/10. Published 2026-02-27.
- How severe is CVE-2026-26861?
- High severity. CVSS v3 base score is 8.3 out of 10.