CVE-2026-5396: Authorization Bypass in Fluent Forms

An attacker exploiting this vulnerability could gain unauthorized access to sensitive form submission data, including personally identifiable information (PII) collected through forms. They could read, modify, or even permanently delete submissions, potentially disrupting business processes or causing data loss. The impact is particularly severe for organizations relying on Fluent Forms to collect critical data, as an attacker could tamper with submissions to manipulate results, gain unauthorized access to user data, or even cause denial of service by deleting submissions. This vulnerability highlights the importance of robust authorization controls, even for users with seemingly limited privileges.

1. 予約済み2026-04-01
2. 公開日2026-05-14

The primary mitigation is to upgrade Fluent Forms to version 6.2.0 or later, which addresses the authorization bypass. If immediate upgrading is not possible, consider restricting access to the Fluent Forms manager role to only essential users. Implement a Web Application Firewall (WAF) rule to block requests containing suspicious formid parameters, particularly those that are excessively long or contain unexpected characters. Regularly review Fluent Forms configurations and user permissions to ensure they adhere to the principle of least privilege. After upgrading, verify the fix by attempting to access a form submission with a spoofed formid parameter; access should be denied.