CVE-2026-100241 in MediaWiki Plugin
Summary
by MITRE • 09/29/2026
Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Wikimedia Foundation Mediawiki - EventBus Extension allows Excavation.
This issue affects Mediawiki - EventBus Extension: 1.47.0-alpha.
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Analysis
by VulDB Data Team • 09/29/2026
The identified vulnerability represents a critical information disclosure flaw within the MediaWiki EventBus extension, specifically affecting version 1.47.0-alpha and potentially earlier iterations depending on deployment configurations. This security issue falls under the category of Exposure of Sensitive Information to an Unauthorized Actor, which is formally classified as CWE-200 in the Common Weakness Enumeration standard. The core technical flaw lies in the extension's handling of event data streams or API responses where sensitive internal state information, configuration details, or user-specific metadata are inadvertently exposed through unfiltered output channels. In a typical MediaWiki deployment utilizing EventBus for real-time updates and inter-service communication, this vulnerability allows an attacker to perform what is known as excavation, a technique wherein the attacker systematically probes various endpoints or event streams to extract valuable data that was not intended for public consumption. The lack of proper access controls or sanitization mechanisms in the extension's response generation logic means that even users with minimal privileges can retrieve detailed internal information about the wiki infrastructure, database schema hints, active session tokens, or other sensitive operational metrics.
From an operational perspective, this vulnerability significantly degrades the security posture of any MediaWiki instance relying on EventBus for its real-time features. The exposure of such data facilitates further reconnaissance activities by malicious actors who can use the leaked information to map out the internal network topology, identify vulnerable components, and craft more targeted attacks against authenticated users or administrative accounts. For example, if session identifiers or cryptographic keys are exposed through these event streams, an attacker could potentially hijack user sessions or decrypt sensitive communications within the platform. This aligns with several tactics in the MITRE ATT&CK framework, particularly T1087 Account Discovery and T1539 Steal Web Session Cookie, as the vulnerability provides a direct pathway to harvesting credentials and session tokens without requiring brute-force attacks or complex exploitation chains. The impact is compounded by the fact that EventBus often operates with elevated privileges to ensure reliable message delivery, meaning that any data leakage through this channel may contain higher-privilege information than what would be available through standard wiki pages.
Mitigation strategies must focus on immediate remediation of the codebase and enhanced monitoring protocols. The primary solution is to upgrade the MediaWiki EventBus extension to a patched version where the developers have implemented strict access controls, ensuring that sensitive fields are either stripped from event payloads or restricted to authorized administrative roles only. If an update is not immediately feasible, administrators should consider disabling the EventBus integration temporarily if it is not critical for core operations, thereby removing the attack vector entirely. Additionally, implementing Web Application Firewall rules can help detect and block anomalous patterns of data extraction attempts that characterize excavation attacks. It is also advisable to review logging configurations to ensure that any successful or attempted exploitation of this vulnerability is captured in audit logs for forensic analysis. Regular security audits focusing on API response filtering and event serialization processes are recommended to prevent similar information leakage issues in future updates, ensuring compliance with OWASP Top 10 guidelines regarding broken access control and sensitive data exposure.