CVE-2026-82851 in Masteriyo LMS Plugin
Summary
by MITRE • 09/12/2026
The Masteriyo LMS WordPress plugin before 3.4.1 does not verify ownership of, or restrict the type of, the records a user requests for download, allowing users with the instructor role to retrieve the full content and metadata of arbitrary posts, including other instructors' private and draft courses.
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Analysis
by VulDB Data Team • 09/12/2026
The vulnerability identified in Masteriyo LMS versions prior to 3.4.1 represents a critical failure in access control mechanisms within the WordPress plugin ecosystem. This flaw specifically affects users assigned the instructor role, who are typically granted elevated privileges for managing course content but should not have unrestricted access to all data stored within the system. The core technical deficiency lies in the absence of proper ownership verification and type restriction when handling requests for downloading records or files associated with posts. Instead of validating that the requesting user is the legitimate owner of the specific post or has explicit permission from the owner, the application processes these download requests based solely on the presence of a valid session token associated with an instructor account. This lack of object-level authorization allows any authenticated instructor to bypass intended security boundaries and access resources belonging to other users.
From a technical perspective, this issue is classified under CWE-284, which describes Improper Access Control, specifically falling into the sub-category of insufficient verification of ownership or permissions for specific objects. The vulnerability exploits the logic used in the backend API endpoints responsible for generating download links or serving file content. When an instructor initiates a request to view course materials, quiz questions, or other educational assets, the server fails to cross-reference the requested resource ID with the user's profile data to ensure ownership. Consequently, by manipulating parameters such as post IDs or record identifiers in HTTP requests, an attacker can enumerate and retrieve sensitive information belonging to arbitrary posts across the entire WordPress installation. This includes not only published content but also private drafts and unpublished courses that are intended to remain invisible to other users until they are explicitly shared or published.
The operational impact of this vulnerability is significant for institutions and educational platforms relying on Masteriyo LMS to manage sensitive academic materials. Instructors can inadvertently expose proprietary course structures, exam questions, and student data if those resources were mistakenly associated with their accounts or if the system allows cross-access due to poor isolation logic. More critically, because draft courses are accessible, competitors or malicious actors could steal intellectual property before it is even released to students. This leads to a severe compromise of confidentiality and integrity within the learning management environment. The ability to retrieve full metadata alongside content means that attackers can gain insights into course titles, descriptions, pricing models, and internal organizational structures, which facilitates further targeted attacks such as social engineering or more precise exploitation of other potential weaknesses in the platform.
This behavior aligns with several tactics defined in the MITRE ATT&CK framework for enterprise environments. It corresponds to T1078, Valid Accounts, as it relies on legitimate instructor credentials to access unauthorized data. Furthermore, it falls under T1530, Data from Cloud Storage Objects, if the course materials are stored externally, or more broadly under T1213, Data from Information Repositories, where an attacker extracts sensitive information from a database-driven application without proper authorization checks. The lack of restriction on record types also suggests potential for data exfiltration beyond just text content, potentially including attached media files if the download mechanism is not strictly scoped to specific file types or locations intended for public consumption.
To mitigate this vulnerability, administrators must immediately upgrade Masteriyo LMS to version 3.4.1 or later, where these access control checks have been implemented and validated by the development team. Until an update can be applied, it is advisable to restrict instructor privileges wherever possible, ensuring that users only have access to courses they explicitly create and manage. Implementing a Web Application Firewall with rules targeting suspicious parameter manipulation in download endpoints may provide temporary relief by blocking requests for arbitrary post IDs. Additionally, auditing user roles and permissions within WordPress ensures that no unnecessary capabilities are granted to the instructor role, reducing the attack surface available to potential attackers who have compromised an instructor account through other means such as credential stuffing or phishing attacks.