CVE-2026-3220

High

Published: 18 May 2026

Published

18 May 2026

Modified

18 May 2026

KEV Added

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Patch

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CVSS Score v3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Score 0.0032 23.9th percentile

Risk Priority 55 floored blend · peak EPSS

Summary

CVE-2026-3220 is a high-severity Cross-site Scripting (CWE-79) vulnerability. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 23.9th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

OWASP Top 10 for Web (2025)

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-30736

Vulnerability details

The Autoptimize WordPress plugin before 3.1.15, Clearfy Cache WordPress plugin before 2.4.2, Speed Optimizer WordPress plugin before 7.7.9 are vulnerable to unauthenticated Stored Cross-Site Scripting (XSS) due to a predictable replacement hash used during the HTML minification process and abusing…

a regular expression. This allows an attacker to inject arbitrary HTML attributes in the final HTML output by anticipating the placeholder format.

CWE(s): CWE-79

Related Threats

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 →

T1189 Drive-by Compromise Initial Access

Adversaries may gain access to a system through a user visiting a website over the normal course of browsing.

attack.mitre.org →

T1059.007 JavaScript Execution

Adversaries may abuse various implementations of JavaScript for execution.

attack.mitre.org →

Why these techniques?

Unauthenticated stored XSS in public-facing WordPress plugins directly enables exploitation of the web application (T1190) to deliver malicious client-side scripts (T1059.007) resulting in drive-by compromise of visitors (T1189).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0