Skip to content
Fencer Vulns
high 8.3

CVE-2026-26862 json

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

published 2026-02-27 8 mo ago modified 2026-06-17 4 mo ago also GHSA-jfrq-hj9f-c8qx , EUVD-2026-9039

cvss
8.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

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

Patch / fix

  • npm clevertap-web-sdk 1.15.3

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
8 mo ago

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/CleverTap/clevertap-web-sdk/issues/442 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L
CNA 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L
GitHub 3.1 8.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L

Affected packages

ecosystem package affected fixed in
npm clevertap-web-sdk
<1.15.3
1.15.3

Classification

Weakness
  • CWE-829 Inclusion of Functionality from Untrusted Control Sphere
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.