WordPress Avada Theme Unauthenticated Arbitrary File Write

The Avada theme for WordPress is vulnerable to Arbitrary File Write in all versions up to, and including, 7.16 when the Fusion Builder plugin is installed and active in versions up to, and including, 3.16. This is due to a chain of authorization and input validation weaknesses across the two components that makes it possible for unauthenticated attackers to write attacker-controlled files to the server. This can be used to create and execute arbitrary PHP files, resulting in remote code execution and complete site compromise. Successful exploitation requires both Avada and Fusion Builder to be installed and active, as well as certain administrator-authored content to be present.

Casky was already ahead

This CVE exploits attack patterns that Casky's 283matched 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 theme for WordPress contains a critical authorization and input validation flaw in conjunction with its Fusion Builder plugin that allows unauthenticated attackers to write arbitrary files to the server. Affecting all versions up to 7.16 of Avada and 3.16 of Fusion Builder, this vulnerability chains multiple weaknesses across components to bypass authentication mechanisms entirely. With a CVSS score of 9.8, the impact is severe: attackers can write malicious PHP files that execute with server privileges, achieving remote code execution and complete server compromise. Organizations using these popular WordPress components are at immediate risk, particularly those without current patching protocols.

Casky.ai's 283 mapped skills detect the attack patterns underlying this vulnerability across MITRE ATT&CK's Privilege Escalation (TA0004) and Credential Access (TA0006) tactics. Practitioners using Casky would identify suspicious POST requests to Fusion Builder endpoints lacking proper authentication checks, followed by file write operations to web-accessible directories—classic indicators of CWE-862 (Missing Authorization). Claude's extended reasoning capability correlates multiple weak signals: missing capability verification, insufficient input sanitization in file path parameters, and absence of access control validation between the theme and plugin components. Security teams would see attack chain patterns showing initial unauthenticated requests followed by PHP file creation in wp-content or plugin directories, enabling them to detect exploitation attempts before code execution 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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Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →

283 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-18431.

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

Access with Stolen Session Cookie

identity access management · low

Run

MITRE ATT&CK Techniques

TA0004 TA0006

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