A critical vulnerability chain in the popular Avada theme for WordPress could allow an unauthenticated attacker to execute arbitrary PHP code on the targeted server. Six distinct security issues are collectively referred to as CVE-2026-18431 and have a critical severity level of 9.8.
The first weakness in the six-step chain allows an attacker to expose user-controlled input to a public request. Combined with some other vulnerabilities, it bypasses checks that would otherwise restrict file writes and their locations.
An attacker could gain full control over the targeted website and do whatever they want, for example, deploy malware, exfiltrate data, redirect users to malicious sites, and create backdoors in the form of administrator accounts.
CVE-2026-18431 affects Avada themes up to version 7.16 and Fusion Builder plugins up to version 3.16, the report states. ThemeFusion, the company behind Avada and Fusion Builder, has released a patch, but Wordfence has not yet disclosed all the details of the vulnerability chain for the benefit of site administrators.
While exploitation of this vulnerability requires the presence of a vulnerable Avada theme, it should be noted that Fusion Builder is a mandatory plugin for Avada, and therefore it is included in all distributions of the theme. This means that the attack surface is not limited in any way, and all sites running on Avada versions up to 7.16 are at risk.
Avada is one of the most popular WordPress products, with more than 1 million sales, so the danger is considerable. In addition to the large volume of traffic, the technical complexity of the vulnerability is significant: Wordfence’s team used its own agentic framework, Argus, to find a six-step vulnerability chain and generate proof-of-concept code for this vulnerability. This process took about two hours from the moment of discovery on July 30.
Wordfence notified ThemeFusion of the vulnerability on August 5, and the company fixed the issues in Avada 7.16.1 and Fusion Builder 3.16.1 on August 10.
The vulnerabilities described in the report show how multiple security weaknesses in one product can be combined to create a complex attack chain that allows an attacker to execute arbitrary PHP code on the server with almost no restrictions. All site administrators using the Avada theme are advised to upgrade to the latest versions to fix CVE-2026-18431.
Read the original article: