CVE-2026-81339 in MasterStudy LMS Plugin
Summary
by MITRE • 09/23/2026
The MasterStudy LMS WordPress Plugin WordPress plugin before 3.7.50 does not perform a per-object ownership check when returning a quiz attempt result, allowing any authenticated user with a minimal (subscriber) role to read other students' quiz grades, pass/fail status and attempt timestamps by referencing an attempt identifier belonging to another user.
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Analysis
by VulDB Data Team • 09/23/2026
The vulnerability identified in MasterStudy LMS WordPress Plugin versions prior to 3.7.50 represents a critical failure in access control mechanisms within the application's backend logic. Specifically, the flaw resides in the API endpoint responsible for retrieving quiz attempt results. When an authenticated user requests data regarding their own or another student's performance on a specific quiz, the system fails to verify that the requesting user has legitimate ownership of the requested resource. This architectural oversight allows any logged-in user with even the most minimal privileges, such as the default subscriber role in WordPress, to bypass intended privacy restrictions and access sensitive academic records belonging to other users.
From a technical perspective, this is classified as an Insecure Direct Object Reference vulnerability, commonly known by its CWE identifier CWE-284. The root cause lies in the server-side processing of HTTP requests where the application trusts client-supplied identifiers without validating them against the session context or database ownership records. By manipulating the attempt identifier parameter sent to the quiz result endpoint, an attacker can iterate through various IDs to retrieve data for different users. This lack of per-object authorization check means that the system does not enforce a binding relationship between the authenticated user's identity and the specific resource being accessed, effectively treating all accessible objects as public within the scope of the API function.
The operational impact of this vulnerability is significant in educational environments where student privacy is paramount. An attacker can systematically harvest quiz grades, pass or fail statuses, and precise timestamps for every attempt made by other students on the platform. This exposure not only violates academic integrity but also constitutes a serious breach of personal data protection regulations such as GDPR or FERPA, depending on the jurisdiction. The ability to correlate specific performance metrics with individual users can lead to targeted harassment, discrimination, or unauthorized profiling of student capabilities and learning patterns without their consent.
To mitigate this risk, administrators must upgrade the MasterStudy LMS plugin to version 3.7.50 or later immediately, as this update includes patches for the identified access control flaw. In addition to applying vendor-provided fixes, it is advisable to implement strict input validation and enforce server-side ownership verification on all API endpoints that return user-specific data. Security teams should also review their WordPress configuration to ensure that only necessary roles have access to LMS-related functionalities and consider implementing Web Application Firewall rules that detect abnormal patterns of sequential ID enumeration typical of this type of exploitation. This incident aligns with the MITRE ATT&CK technique T1078, which covers Valid Accounts used for unauthorized data exfiltration by leveraging legitimate credentials to bypass security controls.