Description

The Secure Custom Fields WordPress plugin before 6.9.4 does not properly verify that a front-end form submission corresponds to the form that was rendered to the visitor, allowing unauthenticated users to submit against a different registered form and modify the title and content of the post that form is bound to.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "3.7",
  "pubDate": "2026-09-19T07:16:33.683Z",
  "pubdate": "2026-09-19T07:16:33.683Z",
  "executiveSummary": "The Secure Custom Fields WordPress plugin, in versions prior to 6.9.4, contains a critical vulnerability categorized as broken access control. This flaw stems from a failure to perform server-side validation of form-binding integrity during front-end submissions. Consequently, unauthenticated attackers can craft arbitrary requests to interact with registered forms they were not intended to access.\nThe impact of this vulnerability is severe, as it permits unauthorized users to modify the title and content of any post associated with a legitimate registered form within the plugin. By manipulating form submission parameters, an attacker can overwrite post data, leading to potential site defacement, unauthorized content injection, or the manipulation of sensitive post meta-information.\nThis vulnerability is particularly dangerous because it does not require prior authentication or elevated privileges, allowing any remote visitor to leverage the plugin's submission endpoints for malicious purposes. The primary risk lies in the integrity and availability of the affected WordPress site's post data. Organizations utilizing this plugin are at risk of data tampering and should prioritize upgrading to version 6.9.4 or later to implement the necessary verification logic for form-submission matching.",
  "technicalDetails": "The root cause of this vulnerability lies in the insecure handling of front-end form submissions, specifically a missing validation layer that verifies the correspondence between the submitted data and the specific form identifier originally rendered to the end-user session. The Secure Custom Fields plugin processes form submissions through a dedicated endpoint, but it fails to cross-reference the incoming request parameters against the server-side configuration that defines the bound post and allowed fields.\nIn a secure implementation, the plugin should associate every rendered form with a unique, cryptographically signed token or a server-side session state that locks the submission to a specific post ID. Instead, the vulnerable versions accept submission parameters that explicitly define the target post ID or form binding without confirming authorization. This design oversight allows an attacker to intercept or reconstruct a legitimate request structure to point toward a different, unintended target.\nThe attack flow proceeds as follows: An attacker identifies the parameters required for a successful form submission via the Secure Custom Fields plugin. By observing the structure of a legitimate request, the attacker can then craft a malicious HTTP POST request. By modifying the identifiers within the request body, the attacker forces the plugin to process the input as if it were a valid submission for a restricted or target-protected form. The server-side logic then proceeds to update the post title and content based on the attacker-supplied input.\nBecause the validation check is absent, the server fails to verify if the attacker has the permission or the context to modify the target resource. The lack of an integrity check between the form definition and the submission process renders the application’s access control model ineffective for front-end operations. This bypass allows for persistent changes to the WordPress database, specifically affecting the 'post_title' and 'post_content' fields of the underlying post objects.\nThe exposure is network-based and does not require the attacker to have an active WordPress user session or specific administrative privileges. The payload behavior involves sending a standard submission packet where the internal form reference has been replaced with the reference of the victim resource. Post-exploitation impact includes unauthorized content modification, which can be leveraged for cross-site scripting (XSS) if the input is later rendered to users, or simply to compromise the integrity of the site's content architecture."
}