CVE-2026-39444 in Series Plugin
Summary
by MITRE • 10/02/2026
Authorization Bypass Through User-Controlled Key vulnerability in PublishPress PublishPress Series organize-series allows Exploiting Incorrectly Configured Access Control Security Levels.This issue affects PublishPress Series: from n/a through 3.1.3.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/02/2026
The identified vulnerability represents a critical authorization bypass within the PublishPress Series plugin, specifically affecting versions ranging from its initial release up to version 3.1.3. This flaw stems from an insecure implementation of access control mechanisms where the system fails to properly validate user permissions against the specific resource being accessed. Instead of relying on robust server-side checks that verify if a logged-in user has administrative privileges or appropriate role-based clearance, the application allows attackers to manipulate input parameters directly tied to object identifiers. By supplying a user-controlled key within these requests, an adversary can trick the backend logic into granting access to restricted content or functionality intended for higher-privileged users. This type of flaw is fundamentally rooted in broken access control principles where the software does not enforce proper separation between authenticated identity and authorized actions on specific data objects.
From a technical perspective, this vulnerability aligns closely with Common Weakness Enumeration identifier CWE-284, which describes Improper Access Control. The core issue lies in how the application handles object references during administrative operations or content management tasks within the series organization features. When a request is made to modify, delete, or view sensitive configuration data for a specific series, the system likely accepts an identifier provided by the client without sufficiently cross-referencing it against the current user's permission set stored in the database session or role metadata. This oversight allows any authenticated user, regardless of their assigned WordPress role such as subscriber, author, or editor, to escalate privileges effectively. The attacker can craft HTTP requests that include manipulated keys pointing to administrative settings or other users' series data, thereby bypassing the intended security boundaries established by the plugin's design.
The operational impact of this vulnerability is severe for any website running an affected version of PublishPress Series. Attackers with even minimal access levels can compromise the integrity and confidentiality of site administration features related to content organization. This could lead to unauthorized modification of series structures, deletion of critical metadata, or exposure of private information associated with specific content groups. In a multi-author environment, this weakness enables lateral movement where lower-privileged users can interfere with the work of administrators or other contributors. Furthermore, because PublishPress is widely used for structuring long-form content and courses, compromising these controls could disrupt site functionality, cause data loss, or serve as an initial foothold for more extensive attacks such as defacement or further exploitation through subsequent injection vectors if the manipulated keys allow access to additional administrative endpoints.
To mitigate this risk, immediate action is required by updating the PublishPress Series plugin to version 3.1.4 or later, where these authorization checks have been corrected to enforce strict validation of user permissions against resource ownership and role requirements. Until an update can be applied, site administrators should consider restricting access to WordPress admin areas using IP whitelisting if feasible, ensuring that only trusted networks can reach administrative endpoints. Additionally, implementing a Web Application Firewall with rules targeting common parameter tampering patterns may provide some layer of defense by blocking requests that attempt to inject suspicious identifiers into series-related API calls or form submissions. Regular auditing of user roles and permissions is also recommended to minimize the attack surface should such vulnerabilities exist in other plugins on the same installation.
This incident highlights the importance of rigorous input validation and authorization checks in all content management system extensions, particularly those handling organizational structures that interact with core administrative functions. Security researchers and developers must ensure that every action triggered by user input is verified against a centralized authority model rather than trusting client-supplied data for access decisions. The ATT&CK framework categorizes this behavior under techniques related to Privilege Escalation and Defense Evasion, specifically where an attacker exploits misconfigured permissions to gain higher-level access without detection. Maintaining up-to-date software components and adhering to secure coding standards that prioritize least-privilege principles are essential strategies for preventing similar authorization bypasses in future developments of WordPress plugins and broader web applications.