CVE-2026-77606 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 `headers=plain`, table header text was emitted into `<th>` via a raw HTML path. User-controlled `mainlabel` content could therefore become executable HTML. Version 7.2.0 fixes the issue.
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Analysis
by VulDB Data Team • 09/18/2026
Semantic MediaWiki is an open-source extension for the MediaWiki platform that enables users to store, manage, and query structured data directly within wiki pages. This functionality allows organizations to build knowledge bases with relational capabilities, supporting complex queries and dynamic content generation. However, prior to version 7.2.0, a critical input validation flaw existed in how table headers were rendered when the output format was set to plain text via the headers parameter. Specifically, the system failed to properly sanitize user-controlled input before embedding it into HTML elements, creating a pathway for cross-site scripting attacks.
The technical vulnerability stems from an improper neutralization of special characters within the mainlabel parameter used in Semantic MediaWiki queries. When a query specifies headers=plain, the application is intended to output table header text without additional formatting or wrapping tags beyond standard HTML structure. Instead of escaping potentially dangerous characters such as angle brackets and quotation marks, the software directly inserted user-supplied content into <th> elements using a raw HTML path. This lack of encoding allowed an attacker who could control the mainlabel input to inject arbitrary JavaScript code that would execute in the context of any victim viewing the resulting page.
This flaw constitutes a classic stored cross-site scripting vulnerability where malicious scripts are permanently stored within target servers, typically as part of database records or wiki pages. The impact is severe because it affects all users who view content containing the crafted query results. Attackers can exploit this to steal session cookies, hijack user accounts, perform actions on behalf of victims, or redirect users to phishing sites. Since Semantic MediaWiki is often used in enterprise and educational environments for collaborative knowledge management, the potential scope of impact extends across entire organizational networks if administrative privileges are compromised through social engineering facilitated by the script execution.
From a classification perspective, this vulnerability aligns with CWE-79: Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. It also maps to MITRE ATT&CK technique T1059.007 which covers JavaScript-based command and control or payload delivery within web applications. The root cause lies in insufficient input validation and output encoding, violating fundamental secure coding principles that require all user-supplied data to be treated as untrusted until explicitly validated and encoded for its specific context.
Mitigation strategies primarily involve upgrading Semantic MediaWiki to version 7.2.0 or later where the issue has been resolved through proper escaping mechanisms. For organizations unable to immediately patch, temporary workarounds include restricting who can execute queries with headers=plain and enforcing strict content policies on mainlabel inputs if possible. Additionally implementing a Web Application Firewall with rules detecting common XSS payloads in query parameters may provide partial protection against exploitation attempts while permanent fixes are deployed. Regular security audits of custom extensions and adherence to OWASP guidelines for input validation will further reduce exposure to similar vulnerabilities in the future.