Vulnerability · Published Feb 27, 2026 · Assigned by mitre

CVE-2026-26861

High 8.3

In plain English

A high-severity security flaw in the clevertap-web-sdk package (npm). Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 11% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.3High

Exploit odds (30 days)0.2%top 89.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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 & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	clevertap-web-sdk	1.15.3	GHSA-j5mf-6rh3-rhgg

Affected products (as reported)

Vendor	Product	Versions
n/a	n/a	n/a

Weakness: CWE-346 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L

In plain English

Official description

Affected packages & fixed versions

Affected products (as reported)

References