CVE-2026-81196 in MasterStudy LMS Plugin
Summary
by MITRE • 09/02/2026
The MasterStudy LMS WordPress Plugin WordPress plugin before 3.7.46 does not properly verify ownership of quiz question identifiers, allowing users with instructor access to read other instructors' quiz questions, including the correct answers and explanations.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified in versions of the MasterStudy LMS WordPress plugin prior to version 3.7.46 represents a critical failure in server-side object ownership verification, specifically within the module handling quiz question management. This flaw stems from an insecure direct object reference mechanism where the application fails to validate that the requesting user possesses administrative or instructor privileges for the specific educational content being accessed. In typical learning management system architectures, data such as quiz questions is associated with a creator ID or course owner ID to enforce isolation between different instructors and courses. However, in this implementation, the backend API endpoints responsible for retrieving question details do not cross-reference the authenticated user's identity against the ownership metadata of the requested resource identifier. This architectural oversight allows any authenticated user holding an instructor role to manipulate parameters such as question IDs or quiz identifiers to access data belonging to other instructors within the same WordPress installation.
From a technical perspective, this issue is classified under CWE-639, which describes Authorization Bypass Through User-Controlled Key. The vulnerability exploits the assumption that possession of a valid session token and an instructor role grants implicit permission to view all content associated with that role level across the entire platform. By simply altering the unique identifier passed in HTTP requests during API calls for question retrieval, attackers can bypass intended access controls. This is not merely a case of missing input validation but a fundamental logic error where authorization checks are either absent or incorrectly implemented at the resource level rather than just the endpoint level. The lack of proper ownership verification means that the application treats all instructor-level users as having global read access to quiz content, disregarding the contextual boundaries established by course enrollment and question creation records in the database.
The operational impact of this vulnerability is severe due to the sensitive nature of the exposed data. Quiz questions often contain not only the problem statements but also correct answers, detailed explanations, grading rubrics, and sometimes proprietary educational material created specifically for a particular institution or client. An attacker with instructor access can systematically enumerate question IDs to scrape entire banks of assessment materials from other instructors. This compromises the integrity of academic assessments by allowing potential cheating if questions are leaked prior to exams. Furthermore, it constitutes a significant breach of confidentiality regarding intellectual property and institutional data privacy policies. In enterprise environments where multiple departments or external partners manage their own training modules, this flaw could lead to unauthorized disclosure of confidential business information embedded within corporate training quizzes.
This vulnerability aligns with the MITRE ATT&CK technique T1078, specifically Valid Accounts, as it relies on legitimate credentials but abuses them through privilege escalation via object manipulation rather than exploiting a software bug in authentication mechanisms. It also relates to CWE-269, Improper Privilege Management, because the system fails to enforce least-privilege principles by granting broader access rights than necessary for the specific task of viewing one's own content. The ability to read other instructors' data effectively elevates the user’s privileges from a scoped instructor role to a global content viewer without any additional authentication steps or explicit authorization checks per resource.
Mitigation strategies must focus on implementing robust server-side ownership verification logic within all API endpoints that handle quiz and question data. Developers should ensure that every request for sensitive resources includes an authorization check that compares the authenticated user's ID against the owner_id field in the database records for questions, quizzes, and courses. Additionally, employing UUIDs instead of sequential integers can mitigate enumeration attacks by making it computationally difficult to guess valid identifiers, although this is a secondary defense since proper access control must remain the primary safeguard. Upgrading to version 3.7.46 or later resolves this issue as the vendor has patched the underlying authorization logic. For organizations unable to upgrade immediately, implementing Web Application Firewall rules that monitor for anomalous patterns in API parameter manipulation and restricting instructor roles to only view content explicitly assigned to their specific course IDs can provide temporary risk reduction until a permanent fix is deployed.