CVE-2026-77608 in Semantic MediaWiki
Summary
by MITRE • 09/18/2026
Semantic MediaWiki is a free, open-source extension to MediaWiki that lets users store and query data within the wiki's pages. Prior to version 7.2.0, when the `value` parameter was reflected back into rendered output and error messaging paths without enough output-context encoding. Version 7.2.0 fixes the issue.
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Analysis
by VulDB Data Team • 09/18/2026
Semantic MediaWiki is a widely deployed extension for the MediaWiki platform that enables structured data storage and querying capabilities within wiki pages, effectively transforming static content into a semi-structured database. The vulnerability identified in versions prior to 7.2.0 represents a critical security flaw rooted in improper output encoding during the rendering of user-supplied input. Specifically, when the value parameter is reflected back into rendered HTML output or error messaging paths, the application fails to apply sufficient context-aware escaping mechanisms. This oversight allows an attacker to inject malicious script code that executes within the victim's browser session whenever they interact with a specially crafted URL or form submission targeting this specific endpoint.
The technical nature of this flaw classifies it as a stored or reflected cross-site scripting vulnerability, depending on whether the injected payload is persisted in the database before being served or executed immediately during request processing. In either scenario, the core issue lies in the lack of proper sanitization and encoding relative to the HTML context where the data appears. When untrusted input containing JavaScript payloads is rendered without adequate transformation into safe entities, the browser interprets these sequences as executable code rather than plain text. This behavior aligns with CWE-79, which defines Improper Neutralization of Input During Web Page Generation, commonly known as Cross-site Scripting (XSS). The absence of robust output encoding creates a direct pathway for client-side attack execution, bypassing standard browser security controls that rely on developers to properly isolate data from code.
The operational impact of this vulnerability is significant due to the potential scope of compromise within an organization's wiki infrastructure. An attacker can exploit this flaw to steal session cookies, hijack user sessions, or perform actions on behalf of authenticated users who view the malicious content. In environments where Semantic MediaWiki manages sensitive organizational data, such as internal documentation, project tracking information, or confidential metrics, XSS attacks could lead to unauthorized access to restricted resources or manipulation of displayed data integrity. Furthermore, if combined with other social engineering techniques, this vulnerability can serve as a vector for phishing campaigns or malware distribution by redirecting users to malicious external sites through crafted links embedded in the reflected output.
Mitigation strategies primarily involve upgrading to Semantic MediaWiki version 7.2.0 or later, where the developers have implemented fixes that enforce strict context-specific encoding on all user-controlled inputs before they are rendered into HTML responses. For organizations unable to upgrade immediately due to compatibility constraints with other extensions or custom code modifications, temporary mitigations include implementing a Web Application Firewall rule set designed to detect and block common XSS payloads in query parameters associated with the affected endpoints. Additionally, developers should review any custom templates or hooks that might bypass core framework encoding functions by manually applying htmlspecialchars or equivalent context-aware escaping routines before outputting data. Regular security audits focusing on input validation and output encoding practices are essential to prevent similar vulnerabilities from arising during future development cycles, ensuring alignment with OWASP Top 10 guidelines regarding injection prevention.