CVE-2026-120561 in JetFormBuilder Plugin
Summary
by MITRE • 11/03/2026
The JetFormBuilder — Dynamic Blocks Form Builder plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the 'do_action' function in the 'Update_Options' action class in all versions up to, and including, 3.6.2. This makes it possible for unauthenticated attackers to modify JetEngine Options Page values when an administrator has configured a form with the "Update Options" post-submission action. The vulnerability requires that both JetFormBuilder and JetEngine are installed and active, and that an administrator has specifically configured a form with the Update Options action.
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Analysis
by VulDB Data Team • 11/03/2026
The identified security flaw resides within the JetFormBuilder plugin for WordPress, specifically affecting versions up to and including 3.6.2 when used in conjunction with the JetEngine plugin. This vulnerability stems from a critical implementation error where the do_action function associated with the Update_Options action class lacks proper capability verification. In secure software architecture, any operation that modifies persistent state or configuration data must strictly enforce authorization checks to ensure only users with appropriate privileges can execute such actions. The absence of this check creates an open pathway for unauthorized actors to interact directly with internal plugin mechanisms without passing through standard WordPress authentication and authorization gates.
From a technical perspective, the core issue is classified as CWE-862 Missing Authorization. When an administrator configures a form within JetFormBuilder to utilize the Update Options post-submission action, they intend for that specific data modification to occur only after legitimate user interaction with the front-end form. However, because the underlying PHP code does not verify if the requester possesses administrative capabilities or any other valid permission set before executing the update logic, this functionality becomes accessible via direct API calls or crafted HTTP requests from unauthenticated sources. The vulnerability effectively bypasses the intended workflow where data submission is tied to a visible user interface element controlled by site administrators.
The operational impact of this flaw allows unauthenticated attackers to arbitrarily modify JetEngine Options Page values. These options often control critical aspects of website behavior, theme settings, or plugin configurations depending on how the administrator has structured their dynamic content strategy. By exploiting this weakness, an attacker can alter these configuration parameters without detection through standard login mechanisms. This could lead to a wide range of adverse outcomes including defacement, disruption of service by altering display logic, or further privilege escalation if specific option values influence access control rules elsewhere in the application stack. The requirement for both JetFormBuilder and JetEngine to be active highlights that this is an integration-level vulnerability where one plugin exposes functionality from another without adequate security boundaries.
In terms of threat modeling, this scenario aligns with ATT&CK technique T1505 Server Software Component which involves installing or configuring additional components on a server to maintain access or expand capabilities. Although the attacker here does not necessarily install new software, they are manipulating existing server-side components and their configuration states through unauthorized means. This falls under the broader category of web application attacks where input validation is insufficient for security-critical operations. The lack of capability checks represents a fundamental failure in implementing secure design principles, specifically failing to enforce least privilege by allowing low-privilege or anonymous entities to perform high-impact administrative functions.
To mitigate this vulnerability, immediate action should be taken by updating the JetFormBuilder plugin to version 3.6.3 or later where the missing capability check has been addressed. Until an update is applied, site administrators can implement a temporary workaround by disabling the Update Options post-submission action in any forms that are publicly accessible. Additionally, implementing Web Application Firewall rules that monitor for unusual patterns of requests targeting known vulnerable endpoints associated with JetEngine and JetFormBuilder interactions can provide an additional layer of defense. It is also advisable to review server logs for signs of unauthorized configuration changes during the window where the vulnerability was present in production environments. Regular security audits focusing on capability checks for all administrative actions exposed through public-facing forms are recommended to prevent similar issues in future plugin updates or custom developments.