CVE-2026-59513 in Masteriyo Plugin
Summary
by MITRE • 07/23/2026
Subscriber Cross Site Scripting (XSS) in Masteriyo - LMS <= 2.3.0 versions.
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Analysis
by VulDB Data Team • 07/23/2026
The vulnerability identified as subscriber cross site scripting in Masteriyo Learning Management System affects versions up to and including 2.3.0, representing a critical security flaw that allows attackers to inject malicious scripts into web pages viewed by other users. This weakness stems from insufficient input validation and output encoding mechanisms within the application's handling of user-submitted data, particularly when processing subscriber information and related parameters. The vulnerability manifests when the system fails to properly sanitize or escape user-controllable inputs before rendering them in web responses, creating an environment where malicious actors can execute arbitrary JavaScript code within the context of other users' browsers.
The technical implementation of this XSS vulnerability occurs through the improper handling of subscriber-related data fields that are directly incorporated into HTML output without adequate sanitization measures. Attackers can exploit this by crafting malicious payloads containing script tags or other executable code that gets stored and subsequently executed when legitimate users view affected pages. The flaw typically resides in areas where user-generated content is displayed without proper context-aware encoding, allowing attackers to bypass security controls designed to prevent such injections. This vulnerability falls under the CWE-79 category of Cross Site Scripting, which specifically addresses the improper sanitization of user-provided data that leads to code execution in victim browsers.
The operational impact of this vulnerability extends beyond simple script execution, potentially enabling attackers to hijack user sessions, steal sensitive information, modify content, or redirect users to malicious sites. When exploited successfully, the XSS attack can compromise the integrity and confidentiality of the learning management system's subscriber data, allowing unauthorized access to course materials, user credentials, and personal information. The vulnerability particularly affects the authentication and authorization mechanisms within Masteriyo, as successful exploitation could lead to privilege escalation or account takeover scenarios where attackers gain unauthorized access to administrative functions or sensitive user data.
Security professionals should recognize this vulnerability as a critical threat vector that aligns with ATT&CK technique T1566.001, which covers spearphishing attacks through social engineering. The attack surface is particularly concerning for educational institutions and training organizations that rely on Masteriyo for their learning management needs, as compromised subscriber accounts could provide attackers with access to entire course catalogs, student records, and institutional data repositories. Organizations should implement immediate mitigations including input validation at multiple layers, output encoding of all user-controllable data, and deployment of web application firewalls to detect and block suspicious script injection attempts.
The recommended remediation approach involves upgrading to Masteriyo versions beyond 2.3.0 where the XSS vulnerability has been addressed through proper input sanitization and output encoding mechanisms. Security teams should also implement comprehensive testing procedures including automated scanning tools and manual penetration testing to verify that all user-controllable inputs are properly sanitized before being rendered in web responses. Additionally, organizations should establish monitoring protocols to detect potential exploitation attempts and maintain regular security updates to protect against similar vulnerabilities. The fix typically involves implementing proper context-aware encoding for HTML, JavaScript, and URL contexts, ensuring that all user-submitted data undergoes validation and sanitization before any processing or display occurs, thereby preventing malicious code execution in the victim's browser environment.