CVE-2026-100377 in MediaWiki
Summary
by MITRE • 09/25/2026
Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Wikimedia Foundation Mediawiki - WikiLambda Extension allows Excavation.
This issue affects Mediawiki - WikiLambda Extension: 1.47.0-alpha. The issue has been remediated on the `master` branch.
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Analysis
by VulDB Data Team • 09/25/2026
The identified vulnerability represents a critical information disclosure flaw within the Wikimedia Foundation's MediaWiki platform, specifically affecting the WikiLambda extension in version 1.47.0-alpha. This security defect 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 involves improper access controls or insufficient data sanitization mechanisms within the WikiLambda extension's codebase. When a user interacts with specific features of this extension, the system inadvertently exposes internal state information, configuration details, or potentially sensitive metadata to entities that lack the necessary privileges to view such data. This exposure is not merely cosmetic but facilitates further exploitation by allowing attackers to map the application's architecture and identify additional attack vectors through systematic excavation of exposed endpoints or response payloads.
The operational impact of this vulnerability extends beyond simple privacy concerns. By leaking internal information, an attacker can perform reconnaissance activities that are essential for planning more sophisticated attacks such as cross-site scripting, SQL injection, or privilege escalation attempts. The ability to excavate sensitive data undermines the integrity and confidentiality guarantees provided by the MediaWiki platform. In a collaborative environment like Wikimedia's projects, where trust among contributors is paramount, such leaks can erode user confidence and potentially expose proprietary editing workflows or internal logic that could be reverse-engineered for malicious purposes. Although this specific instance was found in an alpha release of version 1.47.0-alpha, the underlying architectural weakness suggests a risk to any deployment utilizing similar extension configurations if not properly patched.
Remediation has been addressed on the master branch of the MediaWiki repository, indicating that developers have implemented fixes to restrict access to sensitive data and enforce stricter validation checks before returning information to the client side. Administrators operating instances of MediaWiki with the WikiLambda extension must ensure they are running a version where this patch is applied. It is crucial to verify the exact build number against official release notes or commit logs from the Wikimedia Foundation to confirm that the specific vulnerability related to unauthorized data excavation has been resolved. Additionally, organizations should review their deployment pipelines to prevent alpha versions with known vulnerabilities from being promoted to production environments without adequate security testing and validation processes in place.
From a defensive posture perspective, this incident highlights the importance of continuous integration and delivery security practices within open-source projects. The presence of such flaws in pre-release software underscores the need for rigorous code review procedures that include static analysis tools capable of detecting information leakage patterns aligned with CWE-200. Furthermore, implementing runtime application self-protection mechanisms can help mitigate the impact of similar vulnerabilities by monitoring for anomalous data access patterns. Security teams should also consider adopting a zero-trust architecture model where even internal services and extensions are treated as untrusted until explicitly verified, thereby limiting the blast radius if an information disclosure vulnerability is exploited in future releases.