CVE-2026-5459 Overview
CVE-2026-5459 affects the User Frontend plugin for WordPress, which provides AI-powered frontend posting, user directory, profile, membership, and user registration features. The vulnerability is an Insecure Direct Object Reference [CWE-639] in the payment_page() function. The function fails to validate the user-controlled user_id key, allowing unauthenticated attackers to activate a free subscription pack for any user on the site. This action overwrites an existing paid subscription and causes loss of paid features. All plugin versions up to and including 4.3.1 are affected.
Critical Impact
Unauthenticated attackers can overwrite any user's paid subscription with a free pack, causing loss of paid features across the site.
Affected Products
- WordPress User Frontend plugin versions up to and including 4.3.1
- Sites using paid subscription packs delivered through the plugin
- WordPress installations exposing the plugin's payment endpoint to unauthenticated traffic
Discovery Timeline
- 2026-07-08 - CVE-2026-5459 published to NVD
- 2026-07-08 - Last updated in NVD database
Technical Details for CVE-2026-5459
Vulnerability Analysis
The User Frontend plugin exposes the payment_page() function to handle subscription pack activation. The function accepts a user_id parameter from the request without verifying that the requester owns the account or holds authorization to modify it. An attacker submits an arbitrary user_id value and triggers activation of a free subscription pack against that account. If the target user already has a paid subscription, the activation overwrites the existing pack. The victim loses access to paid features tied to the previous subscription.
The issue is unauthenticated and reachable over the network. Confidentiality is not directly affected, but integrity of subscription state is broken across the site. The flaw is a classic Insecure Direct Object Reference where the identifier is trusted rather than authorized against the current session.
Root Cause
The root cause is missing authorization on a user-controlled key. The payment_page() function reads user_id from the request and acts on the referenced account without a capability check, nonce validation, or ownership comparison against the authenticated session. WordPress conventions require current_user_can() checks and nonce verification for state-changing operations, both of which are absent on this code path.
Attack Vector
An attacker sends a crafted HTTP request to the plugin's payment page endpoint with a targeted user_id value and parameters selecting a free subscription pack. No authentication or user interaction is required. The plugin processes the request as if it originated from the referenced user and replaces their active subscription. Attackers can automate the request across every enumerated user ID to strip paid features from the entire user base. See the Wordfence Vulnerability Report and the WordPress Plugin Changeset for the patched code path.
Detection Methods for CVE-2026-5459
Indicators of Compromise
- Unexpected changes in the wp_usermeta table for keys tied to subscription pack assignment on accounts with prior paid packs.
- HTTP requests to the plugin's payment page endpoint containing a user_id parameter that does not match the authenticated session, including requests from unauthenticated sources.
- User complaints about loss of paid features that correlate to a recent free pack activation event in plugin logs.
Detection Strategies
- Audit plugin activity logs for calls into payment_page() where the user_id value differs from the session user or where no session cookie is present.
- Compare current subscription pack assignments against historical billing records to surface silent downgrades from paid to free packs.
- Alert on bursts of requests to the payment endpoint originating from a single source across multiple user_id values, which indicates enumeration.
Monitoring Recommendations
- Enable WordPress debug logging and a web application firewall in front of /wp-admin/admin-ajax.php and any plugin-exposed payment routes.
- Monitor database writes to subscription metadata and generate an event when a paid pack is replaced with a free pack.
- Retain access logs long enough to reconstruct enumeration patterns against the payment endpoint.
How to Mitigate CVE-2026-5459
Immediate Actions Required
- Update the User Frontend plugin to a version later than 4.3.1 that includes the fix from changeset 3514258.
- Review all user accounts with paid subscription packs and restore any subscriptions that were silently replaced with free packs.
- Restrict network access to the plugin's payment endpoint until the patch is applied.
Patch Information
The vendor addressed the missing authorization in the payment_page() function through the WordPress Plugin Changeset 3514258. Administrators should apply the update through the WordPress plugin dashboard or by deploying the patched plugin package from the official repository.
Workarounds
- Deactivate the User Frontend plugin until the patched version is deployed if paid subscriptions are business-critical.
- Add a web application firewall rule that blocks unauthenticated requests to the plugin's payment endpoint and requests where the user_id parameter does not match the session user.
- Temporarily disable free subscription packs in the plugin configuration to remove the target object of the abuse.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
