WordPress Kirki Plugin Stored XSS via User Metadata

The Kirki – Freeform Page Builder, Website Builder & Customizer plugin for WordPress is vulnerable to Stored Cross-Site Scripting via registration metadata in all versions up to, and including, 6.3.1 This is due to insufficient escaping in `ExceptionalElements::image_element()`, which concatenates a user-meta value straight into an `<img src="…">` attribute. This makes it possible for unauthenticated attackers to inject arbitrary web scripts that execute whenever a user accesses a page rendering a Kirki users collection whose image element is bound to one of the nine registration meta fields. Requires public user registration to be enabled and a published page carrying a `kirki-register` element, which prints the required element nonce into the public markup.

Casky was already ahead

This CVE exploits attack patterns that Casky's 323matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

The Kirki – Freeform Page Builder plugin for WordPress contains a critical stored cross-site scripting (XSS) vulnerability in versions up to 6.3.1. The vulnerability exists in the `ExceptionalElements::image_element()` function, which fails to properly escape user metadata before inserting it directly into HTML image source attributes. This allows unauthenticated attackers to inject malicious JavaScript that persists in the database and executes whenever any user views a page containing the compromised element. WordPress sites using this popular page builder plugin are at significant risk, as the attack requires no authentication and the payload executes in the context of legitimate users viewing the site, potentially leading to credential theft, malware distribution, or unauthorized administrative actions.

Casky's 323 matching skills leverage Claude AI's extended reasoning to identify the attack patterns associated with this vulnerability across two critical MITRE ATT&CK techniques: TA0001 (Initial Access) and TA0043 (Reconnaissance). Practitioners using Casky would observe detection of CWE-79 (Improper Neutralization of Input During Web Page Generation) patterns, specifically flagging instances where user-controlled metadata flows directly into HTML attributes without sanitization. The platform would surface findings showing how attackers probe for unescaped output points in image elements, recognize injection opportunities in registration metadata fields, and track the persistence mechanism through database storage. Security teams would see alerts correlating reconnaissance activity targeting page builder plugins with subsequent attempts to inject script payloads, enabling them to identify compromised accounts and malicious content before widespread exploitation occurs.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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323 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-102173.

Abuse of Public-Facing API: Mobile API Abuse

mobile security · low

Run

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

MITRE ATT&CK Techniques

TA0001 TA0043

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