Stored XSS in WordPress Avada Builder Form Notifications

The Avada (Fusion) Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Form Notification Dynamic-Data action_hook → Media Upload Chain (ID3 Metadata / html_attributes) in all versions up to, and including, 3.16.1 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. Exploitation requires that a Fusion Form is embedded on an admin-authored page (granting manage_options context to the Dynamic Data action hook callback), and that a Post Cards element configured to display attachment post types is present on a publicly accessible page so the planted shortcode payload is rendered.

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 Avada (Fusion) Builder plugin for WordPress contains a stored cross-site scripting (XSS) vulnerability in its Form Notification feature, specifically within the Dynamic-Data action_hook and Media Upload Chain handling of ID3 metadata and HTML attributes. This vulnerability allows unauthenticated attackers to inject malicious JavaScript that persists in the database and executes whenever any user accesses the compromised page. With a CVSS score of 7.2, this poses a significant risk to WordPress sites using Avada—one of the most popular page builders. The vulnerability affects all versions up to 3.16.1 and requires only that a Fusion Form exists on the site, making it exploitable by anyone with access to submit form data, including anonymous visitors.

Casky.ai's 323 matched security skills leverage Claude's extended reasoning to detect attack patterns associated with this vulnerability across MITRE ATT&CK techniques TA0001 (Reconnaissance) and TA0043 (Reconnaissance via information gathering). Practitioners using Casky would identify this threat through skill detections focusing on CWE-79 input validation weaknesses, specifically recognizing unsanitized media file metadata and unescaped HTML attribute outputs in form processing workflows. The platform would flag suspicious DOM manipulation patterns, form submission anomalies, and the characteristic signatures of payload injection through ID3 metadata fields—allowing security teams to pinpoint vulnerable Avada implementations before attackers weaponize the stored XSS for credential harvesting, malware distribution, or session hijacking campaigns.

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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-2026-84938.

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

Investigate the attack patterns behind CVE-2026-84938

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