CVE-2026-26861: CleverTap Web SDK version 1.15.2 and earlier is vulnerable to Cross-Site Scripting (XSS) via window.postMessag

Q: How do I fix CVE-2026-26861?

clevertap web sdk: upgrade to newer than 1.15.2. Exact commands for each OS are on this page.

Q: Is CVE-2026-26861 being exploited?

CVE-2026-26861 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-26861 affect?

CVE-2026-26861 affects clevertap web sdk. Severity is high (CVSS 8.3). 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 v

Q: How urgent is CVE-2026-26861?

Priority 37/100. High severity; Public exploit reference

Routine

HIGH 8.3UPGRADE

CVE-2026-26861 is a high-severity flaw (CVSS 8.3) affecting clevertap web sdk. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	8.3 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 89%)
CISA exploited list	No
Weakness	CWE-346
Published	2026-02-27
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: clevertap

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-02-27 18:16 UTCPublished CVE record published
2026-06-17 10:26 UTCUpdated Record last modified

clevertap clevertap web sdk UPGRADE

Affected: <= 1.15.2

Fixed in: newer than 1.15.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy clevertap-web-sdk || rpm -q clevertap-web-sdk || clevertap-web-sdk --version

2. UPGRADE to newer than 1.15.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade clevertap-web-sdk

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade clevertap-web-sdk

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-26861?

clevertap web sdk: upgrade to newer than 1.15.2. Exact commands for each OS are on this page.

Is CVE-2026-26861 being exploited?

CVE-2026-26861 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-26861 affect?

CVE-2026-26861 affects clevertap web sdk. Severity is high (CVSS 8.3). 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 v

How urgent is CVE-2026-26861?

Priority 37/100. High severity; Public exploit reference

Related CVEs

CVE-2026-26862 HIGH 8.3 UPGRADE CleverTap Web SDK version 1.15.2 and earlier is vulnerable to DOM-based Cross-Site Scripting (XSS) via window.

References

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