CVE-2026-1238

High

Published: 19 March 2026

Published

19 March 2026

Modified

22 April 2026

KEV Added

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Patch

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CVSS Score 7.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

EPSS Score 0.0012 31.1th percentile

Risk Priority 14 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-1238 is a high-severity Cross-site Scripting (CWE-79) vulnerability in Wordpress (inferred from references). Its CVSS base score is 7.2 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 31.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-15 (Information Output Filtering).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

Directly addresses the insufficient input sanitization of the 'fh' parameter, preventing injection of arbitrary web scripts into stored data.

SI-15 Information Output Filtering good match

prevent

Mandates output filtering and escaping to block execution of injected scripts when users access affected pages.

SI-2 Flaw Remediation good match

prevent

Requires timely flaw remediation, such as updating the SlimStat plugin beyond version 5.3.5 to eliminate the stored XSS vulnerability.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1185 Browser Session Hijacking Collection

Adversaries may take advantage of security vulnerabilities and inherent functionality in browser software to change content, modify user-behaviors, and intercept information as part of various browser session hijacking techniques.

attack.mitre.org →

Why these techniques?

Stored XSS in public-facing WordPress plugin directly enables exploitation of the web app (T1190) and facilitates browser session hijacking via injected scripts (T1185).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

The SlimStat Analytics plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'fh' (fingerprint) parameter in all versions up to, and including, 5.3.5 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers…

to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

Deeper analysisAI

CVE-2026-1238 is a stored cross-site scripting (XSS) vulnerability, classified under CWE-79, in the SlimStat Analytics plugin for WordPress. It affects all versions up to and including 5.3.5 due to insufficient input sanitization and output escaping of the 'fh' (fingerprint) parameter. This flaw enables the injection of arbitrary web scripts into pages, which then execute in users' browsers upon access. The vulnerability received a CVSS v3.1 base score of 7.2 (AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N) and was published on 2026-03-19.

Unauthenticated attackers can exploit CVE-2026-1238 over the network with low attack complexity, requiring no privileges or user interaction. By submitting malicious payloads via the 'fh' parameter, they can store scripts on the server that execute whenever any user, including administrators, views the injected page. This achieves low confidentiality and integrity impacts within a changed security scope, such as session hijacking, data theft, or further site compromise.

Advisories and references highlight mitigation through updating the plugin beyond version 5.3.5. Vulnerable code locations include line 185 in admin/view/right-now.php and line 1948 in wp-slimstat.php of tag 5.3.5. A patch is available in changeset 3477417, and additional details appear in Wordfence threat intelligence at the referenced URL.