CVE-2026-116883 in Semantic MediaWiki
Summary
by MITRE • 10/27/2026
Semantic MediaWiki from 3.1.0 before 7.3.1 contains a stored cross-site scripting vulnerability that allows authenticated schema editors to inject HTML through schema descriptions. Attackers with the smw-schemaedit permission can save HTML that is passed unescaped to Html::rawElement() in HtmlBuilder, altering pages and targeting users who view the schema.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security flaw resides within Semantic MediaWiki versions ranging from 3.1.0 up to, but not including, version 7.3.1. This vulnerability is classified as a stored cross-site scripting issue, which represents a significant risk because the malicious payload persists on the server rather than being transiently passed via URL parameters or form inputs. The root cause of this weakness lies in the insufficient sanitization and encoding of user-supplied data when it is rendered for display to other users. Specifically, the vulnerability affects schema descriptions within the wiki environment. When an authenticated user with the smw-schemaedit permission saves a schema description containing HTML code, the system processes this input through Html::rawElement() within the HtmlBuilder component without applying necessary escaping mechanisms. This function explicitly indicates that the content is raw and should not be escaped, which creates a direct pathway for arbitrary script execution if untrusted data is passed to it.
From a technical perspective, the flaw exploits the trust relationship between the application's rendering engine and authenticated users who possess schema editing privileges. Because the input is stored in the database as part of the wiki structure, every subsequent user or administrator who views the affected page will have their browser execute the injected JavaScript code. This persistence distinguishes it from reflected XSS attacks, making it more dangerous as a single injection point can compromise multiple victims over time without requiring further interaction from the attacker beyond the initial submission. The attack vector relies on social engineering to some degree, as the victim must view the page where the malicious schema description is rendered, but once that occurs, the impact is immediate and automatic within the context of the victim's session cookies and privileges.
The operational impact of this vulnerability extends beyond simple script execution. An attacker can leverage the executed JavaScript to perform a variety of malicious actions depending on their objectives. These include stealing sensitive information such as session tokens or authentication cookies, which could lead to account takeover if those accounts have elevated permissions within the wiki environment. Additionally, attackers may use the injected scripts to deface pages by altering content dynamically in the victim's browser view, although this does not change the actual stored data unless combined with other vulnerabilities. In more severe scenarios involving privilege escalation or cross-site request forgery techniques facilitated by the XSS payload, an attacker could potentially perform administrative actions on behalf of a privileged user, thereby compromising the integrity and availability of the entire wiki instance.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-79, which covers Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The specific mechanism involving stored payloads maps to CWE-80 in many contexts where persistence is key, though broadly it falls under the general category of input validation failures. In terms of the MITRE ATT&CK framework for enterprise security, this behavior corresponds to techniques such as T1059 Command and Control Scripting or potentially T1204 User Execution if the payload tricks users into clicking links that trigger further exploitation chains. It also relates to data manipulation aspects found in persistence mechanisms where attacker-controlled content is embedded within legitimate application structures.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The primary solution is to upgrade Semantic MediaWiki to version 7.3.1 or later, as the developers have patched this specific issue by ensuring that schema descriptions are properly escaped before being passed to rendering functions like Html::rawElement(). For organizations unable to patch immediately due to compatibility constraints with other extensions or custom code, a temporary workaround involves restricting the smw-schemaedit permission to only highly trusted administrators rather than regular authenticated users. This reduces the attack surface significantly by limiting who can inject persistent malicious content into schema descriptions. Additionally, implementing strict Content Security Policy headers that restrict script execution sources and disable inline scripts where possible can mitigate the impact of any successfully injected XSS payloads by preventing them from executing in the victim's browser context. Regular security audits focusing on input validation practices across all user-editable fields are also recommended to prevent similar vulnerabilities arising from other components within the application stack.