CVE-2026-39444 Overview
CVE-2026-39444 is an Insecure Direct Object Reference (IDOR) vulnerability in the PublishPress Series plugin for WordPress, formerly known as organize-series. The flaw allows authenticated attackers to bypass authorization controls by manipulating user-controlled keys that reference internal objects. Affected versions include PublishPress Series up to and including 3.1.3. The weakness is tracked under [CWE-639: Authorization Bypass Through User-Controlled Key].
Critical Impact
Authenticated users with low-level privileges can access or modify series objects belonging to other users, resulting in limited integrity and availability impact across the WordPress site.
Affected Products
- PublishPress Series (organize-series) plugin for WordPress
- Versions from n/a through 3.1.3
- WordPress sites running the vulnerable plugin with authenticated low-privilege users
Discovery Timeline
- 2026-10-02 - CVE-2026-39444 published to the National Vulnerability Database (NVD)
- 2026-10-02 - Last updated in NVD database
Technical Details for CVE-2026-39444
Vulnerability Analysis
The PublishPress Series plugin manages post series within WordPress, exposing endpoints that act on series identifiers supplied by the client. The vulnerable code paths accept object identifiers from request parameters without verifying that the authenticated user owns or has permission to act on the referenced object. An attacker holding a low-privilege account can substitute identifiers belonging to other users and invoke operations that should be restricted.
This class of flaw is categorized as Insecure Direct Object Reference and falls under [CWE-639]. The root issue is an incorrectly configured access control security level, where authentication is enforced but per-object authorization is missing. Successful exploitation does not expose sensitive confidential data, but it enables unauthorized modification and limited disruption of plugin-managed content.
Root Cause
The plugin relies on user-supplied keys, such as series IDs, to locate records and perform actions. The access control layer confirms that the requester is authenticated but omits a check that the requester owns the target object or holds a capability sufficient to act on it. This gap between authentication and authorization is the direct cause of the bypass.
Attack Vector
Exploitation requires a network-reachable WordPress instance and valid low-privilege credentials, such as a subscriber or contributor account. The attacker sends crafted HTTP requests to plugin endpoints, substituting the target object identifier. No user interaction is required. The scope is unchanged, with limited impact to integrity and availability of PublishPress Series data. See the Patchstack Vulnerability Report for additional technical context.
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Stop Identity AttacksDetection Methods for CVE-2026-39444
Indicators of Compromise
- Unexpected modifications to series records in the WordPress database, particularly rows owned by administrators or editors but altered by low-privilege accounts.
- WordPress audit log entries showing low-privilege users invoking PublishPress Series actions against objects they did not create.
- Repeated HTTP requests to organize-series endpoints with sequentially enumerated identifier parameters.
Detection Strategies
- Review web server access logs for authenticated requests to PublishPress Series admin-ajax or REST endpoints referencing object IDs outside the requester's ownership.
- Correlate WordPress user activity logs with database writes to series tables to identify authorization anomalies.
- Deploy a Web Application Firewall (WAF) rule to flag enumeration patterns against plugin endpoints.
Monitoring Recommendations
- Enable verbose logging in WordPress and the PublishPress Series plugin to capture user, action, and target object identifiers.
- Forward WordPress logs to a centralized SIEM or data lake for correlation and historical analysis.
- Alert on bursts of 4xx or 2xx responses from plugin endpoints originating from accounts with subscriber or contributor roles.
How to Mitigate CVE-2026-39444
Immediate Actions Required
- Upgrade PublishPress Series to a version later than 3.1.3 once the vendor publishes a fix.
- Audit WordPress user accounts and remove or disable unused low-privilege accounts that could be leveraged for exploitation.
- Rotate credentials for any accounts suspected of unauthorized use.
Patch Information
At the time of publication, the vulnerability affects PublishPress Series through version 3.1.3. Administrators should monitor the Patchstack Vulnerability Report and the plugin's WordPress.org page for a patched release and apply updates promptly.
Workarounds
- Temporarily deactivate the PublishPress Series plugin on sites that allow untrusted user registration until a fix is available.
- Restrict access to WordPress authenticated endpoints behind IP allowlists or VPN controls where feasible.
- Enforce the principle of least privilege by limiting role assignments and disabling open user registration.
# Configuration example: disable open registration and deactivate the plugin via WP-CLI
wp option update users_can_register 0
wp plugin deactivate organize-series
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
