VulnerabilityPublished 27 Feb 2026

CVE-2026-26861: clevertap-web-sdk · Origin Validation Error

Affects clevertap-web-sdkSource CVE Database V5

Not known to be exploited · CVSS 8.3 High.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

8.3High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
GitHubclevertap/clevertap-web-sdk`pkg:github/clevertap/clevertap-web-sdk`Other threats	Affected <=1.15.2	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate CVE-2026-26861, organizations should first verify if their web applications use CleverTap Web SDK version 1.15.2 or earlier. If so, they should seek an updated SDK version from CleverTap that addresses the origin validation flaw or apply vendor-provided patches once available. In the absence of an official patch, developers should implement strict origin validation by replacing the includes() method with exact origin matching, such as using strict equality checks against a whitelist of trusted origins. Additionally, web applications should employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS attacks. Developers can also sanitize and validate all inputs and messages received via postMessage to ensure they conform to expected formats. Monitoring and logging postMessage events can help detect suspicious activity. Finally, educating development teams about secure handling of cross-origin communications and conducting regular security code reviews focused on message handling functions will help prevent similar vulnerabilities.

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

Impact

The impact of CVE-2026-26861 on organizations worldwide can be substantial. Successful exploitation allows attackers to execute arbitrary scripts in the security context of the affected web application, potentially leading to the compromise of user credentials, session hijacking, unauthorized actions on behalf of users, and data exfiltration. This undermines the confidentiality and integrity of user data and can damage the reputation and trustworthiness of affected organizations. Additionally, attackers could use the vulnerability to deliver further malware or conduct phishing attacks by manipulating the web application's content. Since CleverTap is a widely used customer engagement and analytics platform integrated into many web applications, the scope of affected systems can be broad, impacting industries such as e-commerce, finance, media, and technology. The vulnerability could also be leveraged as a foothold for more advanced attacks within enterprise environments. The absence of a patch increases the risk window, and organizations that do not implement mitigations remain exposed. Overall, the vulnerability poses a high risk to the security posture of organizations relying on the CleverTap Web SDK.

CWE-346Origin Validation Error (opens in a new tab)
Class weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not properly verify that the source of data or communication is valid.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V14.5.2 (opens in a new tab)
V14.5.3 (opens in a new tab)
V1.4.4 (opens in a new tab)
Attack patterns
JSON Hijacking (aka JavaScript Hijacking) (opens in a new tab)
Cache Poisoning (opens in a new tab)
DNS Cache Poisoning (opens in a new tab)
Exploit Script-Based APIs (opens in a new tab)
Application API Message Manipulation via Man-in-the-Middle (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 27 Feb 2026, 17:43 UTC

WeaknessesCWE-346

Technical details

References

Community reviews

Related threats