CVE-2026-3876
Published: 16 April 2026
Summary
CVE-2026-3876 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 10.3th 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).
Deeper analysis
CVE-2026-3876 is a stored cross-site scripting (XSS) vulnerability in the Prismatic plugin for WordPress, affecting all versions up to and including 3.7.3. The flaw stems from insufficient input sanitization and output escaping of user-supplied attributes within the 'prismatic_decode' function when handling the 'prismatic_encoded' pseudo-shortcode, as detailed in the CVE description published on 2026-04-16.
Unauthenticated attackers can exploit this vulnerability by submitting a comment containing a crafted 'prismatic_encoded' pseudo-shortcode on a vulnerable page or post. Whenever a user accesses the injected page, the arbitrary web scripts execute in their browser context. The CVSS v3.1 base score is 7.2 (AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N), reflecting a high-severity issue tied to CWE-79 (Cross-Site Scripting).
Advisories point to mitigation via updating the Prismatic plugin to version 3.7.4 or later. The WordPress plugin trac changeset compares prismatic-core.php between tags 3.7.3 and 3.7.4, highlighting the patch. Further details are provided in the Wordfence threat intelligence entry.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-23212
Vulnerability details
The Prismatic plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'prismatic_encoded' pseudo-shortcode in all versions up to, and including, 3.7.3. This is due to insufficient input sanitization and output escaping on user-supplied attributes within the 'prismatic_decode' function.…
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This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page by submitting a comment containing a crafted 'prismatic_encoded' pseudo-shortcode.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Stored XSS in public-facing WordPress plugin directly enables exploitation of the web application (T1190) and execution of arbitrary JavaScript in victim browsers (T1059.007).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires validation of user-supplied input such as comments containing the 'prismatic_encoded' pseudo-shortcode to prevent injection of malicious scripts.
Mandates output filtering and escaping in the 'prismatic_decode' function to block execution of injected scripts when pages are accessed.
Ensures timely remediation of the flaw by updating the Prismatic plugin to version 3.7.4 or later, directly addressing the sanitization and escaping deficiencies.