CVE-2026-57736: HubSpot Information Disclosure Flaw

CVE-2026-57736 Overview

CVE-2026-57736 is a sensitive information disclosure vulnerability affecting the HubSpot plugin (Leadin) for WordPress. The flaw allows authenticated users with low privileges to retrieve embedded sensitive data that should not be exposed through the plugin's data flows. The issue is categorized under CWE-201: Insertion of Sensitive Information Into Sent Data. The vulnerability affects all HubSpot plugin versions up to and including 11.3.51. Successful exploitation exposes confidential information tied to the plugin's marketing, lead capture, and CRM integration features.

Critical Impact
Authenticated attackers with low privileges can retrieve sensitive data embedded in the WordPress HubSpot plugin, potentially exposing CRM records, marketing configuration, and lead information across a scoped boundary.

Affected Products

HubSpot Plugin for WordPress (Leadin) versions through 11.3.51
WordPress sites integrating HubSpot CRM, forms, and marketing analytics via the Leadin plugin
Any deployment exposing the plugin's endpoints to authenticated low-privilege users

Discovery Timeline

2026-07-01 - CVE-2026-57736 published to NVD
2026-07-01 - Last updated in NVD database

Technical Details for CVE-2026-57736

Vulnerability Analysis

The vulnerability stems from the plugin embedding sensitive information into data returned to authenticated users. Attackers with valid low-privilege credentials on the WordPress instance can invoke plugin functionality that discloses information beyond their authorization scope. The scope-changed nature of the flaw indicates that the exposed data crosses a security boundary, affecting resources managed outside the vulnerable component. The attack requires network access and no user interaction, making automated exploitation practical once valid credentials are obtained.

Root Cause

The root cause is classified under [CWE-201]: Insertion of Sensitive Information Into Sent Data. The plugin includes confidential fields, tokens, or CRM-linked records in responses transmitted to users who should not receive them. Proper filtering, redaction, or authorization checks on outbound data are missing or incomplete in versions up to 11.3.51. This design pattern violates the principle of least exposure for API and endpoint responses.

Attack Vector

Exploitation requires network access to the WordPress site and authenticated access with low privileges. Once authenticated, the attacker sends crafted requests to plugin endpoints that return responses containing sensitive embedded data. No social engineering or user interaction is required to trigger the disclosure. The attack works against default installations of vulnerable versions and can be scripted for broad reconnaissance across affected sites. Refer to the Patchstack Vulnerability Report for technical details.

Detection Methods for CVE-2026-57736

Indicators of Compromise

Unusual authenticated requests from low-privilege accounts to HubSpot plugin endpoints under /wp-admin/admin-ajax.php or plugin REST routes
Anomalous response sizes from leadin plugin routes suggesting bulk data extraction
Access patterns from accounts that historically do not interact with CRM or marketing plugin features

Detection Strategies

Audit WordPress access logs for repeated requests to Leadin plugin endpoints originating from subscriber, contributor, or author roles
Correlate authentication events with plugin API calls to identify credential-driven reconnaissance
Compare installed plugin version against 11.3.51 to identify vulnerable hosts across the estate

Monitoring Recommendations

Enable verbose logging on the WordPress REST API and audit responses for embedded PII or CRM identifiers
Alert on high-volume plugin endpoint access from any single authenticated session
Monitor for newly created low-privilege accounts followed by plugin API activity

How to Mitigate CVE-2026-57736

Immediate Actions Required

Update the HubSpot (Leadin) WordPress plugin to a version above 11.3.51 as soon as the vendor releases a fix
Review and prune low-privilege WordPress accounts, removing unused or unnecessary users
Rotate any HubSpot API keys or integration tokens that may have been exposed through the plugin

Patch Information

At the time of publication, the Patchstack advisory indicates the vulnerability affects HubSpot plugin versions through 11.3.51. Administrators should consult the Patchstack Vulnerability Report and the HubSpot plugin changelog for the fixed release and apply updates through the WordPress plugin manager.

Workarounds

Restrict access to the WordPress admin and REST API endpoints using IP allowlists or a web application firewall
Temporarily deactivate the HubSpot (Leadin) plugin until a patched version is installed if sensitive CRM data is stored
Enforce strong authentication and multi-factor authentication on all WordPress user accounts to reduce the risk of low-privilege credential abuse

bash

# Configuration example: identify vulnerable HubSpot plugin installations
wp plugin get leadin --field=version
# If output is <= 11.3.51, update immediately:
wp plugin update leadin