CVE-2026-116882 in Semantic MediaWiki
Summary
by MITRE • 10/27/2026
Semantic MediaWiki from 4.2.0 before 7.3.1 contains a stored cross-site scripting vulnerability that allows authenticated profile or schema editors to inject HTML through FacetedSearch exploration-link labels. Attackers can store markup in the label, which ExploreListBuilder::buildHTML() passes unescaped to Html::rawElement(), altering the Special:FacetedSearch page and potentially running scripts in viewers' browsers.
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Analysis
by VulDB Data Team • 10/27/2026
The vulnerability identified in Semantic MediaWiki versions prior to 7.3.1 represents a significant security flaw within the Faceted Search functionality, specifically classified as a stored cross-site scripting (XSS) issue. This weakness arises from improper input validation and output encoding mechanisms when handling user-supplied data for exploration-link labels. The core technical failure lies in how the application processes these labels during the rendering of search results. When an authenticated user with profile or schema editing privileges creates or modifies a facet, they can inject malicious HTML markup into the label field. This data is then persisted within the database without adequate sanitization. Subsequently, when another user accesses the Special:FacetedSearch page to view these facets, the system retrieves this stored payload and passes it directly to Html::rawElement() via ExploreListBuilder::buildHTML(). Because rawElement indicates that the content should be treated as safe HTML rather than plain text, the browser interprets the injected markup as executable code. This architectural oversight allows an attacker who has write access to schema or profile configurations to plant persistent scripts on pages viewed by other users, effectively turning a legitimate administrative feature into a vector for client-side attacks.
From a technical perspective, this vulnerability aligns with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The specific subtype here is stored XSS, where the malicious script is saved on the target server and executed whenever a victim accesses the affected page. This differs from reflected XSS in that the payload does not need to be delivered via a crafted link; it resides permanently until removed by an administrator. Furthermore, this flaw can be mapped to MITRE ATT&CK technique T1059.007, which covers JavaScript execution under client-side scripting. The attack chain begins with privilege abuse, requiring the attacker to possess specific permissions such as profile editing or schema modification rights within Semantic MediaWiki. Once these privileges are obtained, the attacker crafts a malicious label containing script tags or event handlers like onload or onerror. When the FacetedSearch module renders the interface for any user browsing those facets, the browser executes the embedded JavaScript in the context of the vulnerable website. This allows the attacker to perform actions such as stealing session cookies, hijacking user sessions, performing unauthorized actions on behalf of the victim, or defacing the application interface.
The operational impact of this vulnerability is substantial due to its persistent nature and the specific privileges required for exploitation. While it requires authentication, Semantic MediaWiki deployments often involve collaborative environments where multiple users have editing rights over schemas and profiles. If an attacker compromises a low-privilege account with schema-editing capabilities or exploits social engineering to gain such access, they can establish a long-term foothold within the application's client-side environment. The impact extends beyond simple script execution; it facilitates session hijacking which could lead to full account takeover if secure cookie flags are not properly configured on the server side. Additionally, because the payload is stored in the database, every user who views the affected facet becomes a potential victim without any direct interaction with the attacker's initial exploit vector other than loading the page. This increases the blast radius significantly compared to non-persistent vulnerabilities. In enterprise settings where Semantic MediaWiki might be integrated into larger knowledge management systems or intranets, this could serve as an entry point for further lateral movement if session tokens are shared across services or if sensitive data is displayed on pages that also render these facets.
Mitigation strategies must address both the immediate technical flaw and broader security hygiene practices. The primary remediation involves upgrading Semantic MediaWiki to version 7.3.1 or later, where this specific input validation issue has been resolved by ensuring that exploration-link labels are properly escaped before being passed to HTML rendering functions. For organizations unable to upgrade immediately due to compatibility constraints with other extensions or dependencies, a temporary workaround is essential. Administrators should restrict the profile and schema editing privileges to only those users who absolutely require them, adhering to the principle of least privilege. Implementing a Web Application Firewall (WAF) with rules tuned to detect common XSS payloads in POST requests targeting FacetedSearch endpoints can provide an additional layer of defense by blocking malicious inputs before they reach the application logic. Furthermore, enabling Content Security Policy headers on the web server hosting Semantic MediaWiki can mitigate the impact of successful exploitation by restricting the sources from which scripts are allowed to execute and preventing unauthorized data exfiltration via cross-origin requests. Regular security audits focusing on input validation across all user-editable fields within the wiki structure are also recommended to identify similar vulnerabilities in other modules that may handle raw HTML rendering without adequate sanitization.