CVE-2026-88828: Blacklist Manager Auth Bypass Vulnerability

CVE-2026-88828 Overview

The Blacklist Manager for WooCommerce WordPress plugin contains an authentication bypass flaw affecting versions 1.3.0 through 2.3.1. The plugin fails to enforce user blocking across every authentication path. A blocked account can continue authenticating and retain its original privileges without the block being enforced or logged. The weakness is tracked under [CWE-288: Authentication Bypass Using an Alternate Path or Channel].

Critical Impact
Site owners who rely on the plugin to revoke access cannot trust that a blocked account is actually denied. Blocked users keep operating with their granted privileges on affected WooCommerce stores.

Affected Products

Blacklist Manager for WooCommerce WordPress plugin, version 1.3.0
Blacklist Manager for WooCommerce WordPress plugin, versions 1.3.0 through 2.3.1
WordPress sites running WooCommerce with the affected plugin installed

Discovery Timeline

2026-09-28 - CVE-2026-88828 published to NVD
2026-09-28 - Last updated in NVD database

Technical Details for CVE-2026-88828

Vulnerability Analysis

The plugin implements a user blocking feature intended to prevent specific accounts from logging in or interacting with the store. The block check is attached to some but not all authentication paths exposed by WordPress and WooCommerce. Authentication endpoints that skip the check accept the blocked account's credentials and issue a valid session.

Because the alternate authentication paths bypass the enforcement logic, no block event is recorded. Site owners reviewing plugin logs see no indication that the account continued to access the site. The flaw affects confidentiality and integrity because the attacker operates with the account's existing WooCommerce privileges, which can include customer data access or order modification.

Root Cause

The root cause is incomplete coverage of authentication hooks. The plugin filters the primary WordPress login flow but omits other entry points that WordPress and WooCommerce expose, such as programmatic authentication, cookie-based session restoration, or REST API authentication. [CWE-288] describes this pattern as an authentication bypass using an alternate path.

Attack Vector

The attack requires a valid account that the site owner has already blocked using the plugin. The attacker authenticates through an authentication path that the plugin does not intercept. The server returns a valid session, and the attacker reuses the account's privileges. Refer to the WPScan Vulnerability Report for technical details.

Detection Methods for CVE-2026-88828

Indicators of Compromise

Successful authentication events for user accounts that administrators previously added to the plugin's blocklist.
WooCommerce order activity, cart changes, or profile updates originating from accounts marked as blocked.
Absence of block enforcement entries in plugin logs despite blocked accounts remaining active on the site.

Detection Strategies

Correlate the plugin's blocklist against WordPress authentication logs to flag any login from a blocked user ID or email.
Monitor REST API and XML-RPC authentication endpoints for sessions tied to accounts present in the blocklist.
Compare WooCommerce customer activity against the current blocklist to find accounts that should not be transacting.

Monitoring Recommendations

Forward WordPress authentication and WooCommerce order logs to a centralized log store for retention and query.
Alert on any session establishment or privileged action by a user ID that appears in the plugin's blocklist table.
Baseline session cookie reuse and REST API token usage for blocked accounts to detect persistent access.

How to Mitigate CVE-2026-88828

Immediate Actions Required

Inventory WordPress sites running the Blacklist Manager for WooCommerce plugin and identify installations in the 1.3.0 to 2.3.1 range.
Update the plugin to a version released after 2.3.1 that enforces blocking on every authentication path.
Reset credentials and invalidate active sessions for accounts the site owner has blocked to terminate any existing authenticated sessions.

Patch Information

Consult the WPScan Vulnerability Report for the fixed version and vendor remediation guidance. Apply the vendor-supplied update as the primary remediation.

Workarounds

Delete or demote the WordPress user account instead of relying on the plugin's block feature until the patched version is deployed.
Change the account's email and force a password reset to invalidate credential-based authentication paths.
Restrict REST API and XML-RPC authentication at the web server or WAF layer for accounts that must remain blocked.

bash

# Configuration example
# Force logout of a specific blocked user by destroying their sessions via WP-CLI
wp user session destroy <user_id> --all

# Optionally change the user role to no access until the plugin is patched
wp user set-role <user_id> no_access