CVE-2026-86834: MetForm WordPress Information Disclosure

CVE-2026-86834 Overview

CVE-2026-86834 affects the MetForm WordPress plugin in versions before 4.3.1. The plugin writes a debug file to the web root on every form submission when the HubSpot Forms integration is enabled. The plugin does not restrict access to this file, allowing unauthenticated attackers to retrieve its contents over the network.

The exposed file contains upstream API response data, including correlation identifiers and cookies returned by HubSpot. This weakness is classified under Information Exposure [CWE-200].

Critical Impact
Unauthenticated remote attackers can read debug artifacts containing third-party API correlation identifiers and cookies written to the WordPress web root.

Affected Products

MetForm WordPress plugin versions prior to 4.3.1
WordPress sites with the MetForm HubSpot Forms integration enabled
Any public-facing deployment where the plugin writes to a reachable web root

Discovery Timeline

2026-10-03 - CVE-2026-86834 published to the National Vulnerability Database (NVD)
2026-10-06 - Last updated in NVD database

Technical Details for CVE-2026-86834

Vulnerability Analysis

MetForm writes a diagnostic file into the WordPress web root each time a form is submitted while the HubSpot Forms integration is active. The file captures the upstream HTTP response returned by the HubSpot API, including correlation identifiers and Set-Cookie values associated with the integration.

Because the file is placed under the document root with no access control, directory indexing restriction, or randomized naming documented in the advisory, any unauthenticated client that can reach the WordPress host can request it directly. The disclosed material can aid session correlation, request replay against HubSpot, and reconnaissance of integration behavior.

Root Cause

The root cause is improper placement of a debug artifact combined with missing access control. The plugin writes sensitive upstream response data to a web-reachable location rather than a protected directory such as wp-content/uploads with .htaccess hardening or a path outside the document root. No authentication or capability check guards the resulting URL.

Attack Vector

An unauthenticated attacker triggers or waits for a legitimate form submission that exercises the HubSpot integration. The attacker then issues an HTTP GET request against the predictable debug file path in the web root to retrieve its contents. Successful exploitation yields HubSpot correlation identifiers and cookies without any user interaction on the WordPress site. Technical specifics are available in the WPScan Vulnerability Report.

Detection Methods for CVE-2026-86834

Indicators of Compromise

Unexpected files written to the WordPress web root that contain HubSpot API response bodies, headers, or Set-Cookie values
Unauthenticated HTTP GET requests from external addresses targeting debug file paths under the site root
Access log entries showing repeated retrieval of the same debug artifact by non-browser user agents

Detection Strategies

Scan the WordPress document root for files created immediately after form submissions when the HubSpot integration is enabled
Compare installed MetForm plugin versions against 4.3.1 across managed WordPress hosts
Alert on web server responses that serve files containing substrings associated with HubSpot API responses, such as correlation identifier headers

Monitoring Recommendations

Ingest WordPress access logs into a centralized log platform and alert on anonymous reads of files in the web root with suspicious extensions
Monitor file creation events in the WordPress root directory using host-based integrity monitoring
Track outbound HubSpot API traffic and correlate with new files appearing in the document root

How to Mitigate CVE-2026-86834

Immediate Actions Required

Upgrade the MetForm WordPress plugin to version 4.3.1 or later on all affected sites
Delete any debug files already written to the WordPress web root by vulnerable versions
Rotate any HubSpot API credentials, portal tokens, or cookies that may have been exposed in the debug artifacts

Patch Information

The vendor fixed the issue in MetForm version 4.3.1. Review the WPScan Vulnerability Report for advisory details and version guidance before deploying.

Workarounds

Disable the HubSpot Forms integration in MetForm until the plugin is upgraded
Add a web server rule to deny direct access to the debug file path in the WordPress web root
Restrict directory listing and block unauthenticated reads of unknown files under the site root at the reverse proxy or WAF layer

bash

# Example nginx rule to block access to MetForm debug artifacts in the web root
location ~* /metform.*\.(log|txt|json)$ {
    deny all;
    return 404;
}