CVE-2026-82846 in LMS Plugin
Summary
by MITRE • 09/05/2026
The Masteriyo LMS WordPress plugin before 3.4.0 does not sanitise and escape some course settings before outputting them in a page available to all visitors, allowing users with a course-author role to perform Stored Cross-Site Scripting attacks that run in the session of anyone viewing the course, including a logged-in administrator.
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Analysis
by VulDB Data Team • 09/05/2026
The vulnerability identified within Masteriyo LMS WordPress plugin versions prior to 3.4.0 represents a critical security flaw rooted in inadequate input validation and output encoding mechanisms. Specifically, the application fails to properly sanitize or escape specific course settings before rendering them on public-facing pages accessible to all visitors without authentication requirements. This architectural oversight creates an environment where malicious actors can inject executable scripts into data fields that are subsequently displayed to users. The core technical deficiency lies in the absence of robust output encoding practices for dynamic content derived from user-controlled inputs, a fundamental principle often overlooked during rapid development cycles but essential for maintaining web application integrity against injection-based attacks.
This flaw enables Stored Cross-Site Scripting, commonly referred to as persistent XSS, which is classified under CWE-79 in the Common Weakness Enumeration standard. Unlike reflected XSS where malicious payloads are delivered via direct links, stored vulnerabilities persist within the target server's database or file system. In this specific context, an attacker with a course-author role can embed JavaScript code into course settings such as titles, descriptions, or custom fields. When these pages are loaded by any visitor, including administrators, the browser executes the injected script in the security context of the website domain. This persistence ensures that every user accessing the compromised content is exposed to the malicious payload without requiring additional social engineering tactics beyond initial access to the authoring interface.
The operational impact of this vulnerability is severe due to its ability to compromise high-privilege accounts through lower-privileged entry points. Since the affected pages are available to all visitors, any individual can trigger the execution of the stored script by simply viewing a compromised course page. If an administrator or other privileged user views such a page while logged in, their session cookies and authentication tokens become accessible to the attacker's malicious script. This allows for complete account takeover, where the attacker can perform actions on behalf of the victim, modify site configurations, steal sensitive data, or further propagate malware across the network. The ability to escalate privileges from a standard course-author role to full administrative control significantly amplifies the risk profile and potential damage associated with this vulnerability.
From an offensive security perspective, this attack vector aligns closely with techniques documented in the MITRE ATT&CK framework, particularly those involving client-side code injection and session hijacking. The exploitation path typically involves crafting a payload that exfiltrates cookies or performs actions via Cross-Site Request Forgery mechanisms enabled by the stolen credentials. This highlights the importance of understanding how role-based access control intersects with input validation layers; even if an attacker has limited permissions, insufficient sanitization can lead to disproportionate consequences for the entire system ecosystem.
Mitigation strategies must focus on implementing strict output encoding and context-aware escaping techniques immediately upon rendering user-supplied data into HTML contexts. Developers should utilize established libraries that handle XSS prevention automatically rather than relying on manual filtering which is prone to bypasses. Additionally, enforcing Content Security Policy headers can provide a layer of defense by restricting the sources from which scripts are allowed to execute, thereby mitigating the impact even if an injection occurs. Upgrading to version 3.4.0 or later resolves this issue as it includes patches for these sanitization failures. Organizations relying on earlier versions should prioritize immediate updates and conduct thorough code reviews to identify similar patterns of insecure data handling across other plugins and themes within their WordPress infrastructure.