CVE-2026-103046 in MediaWiki
Summary
by MITRE • 09/30/2026
Improper neutralization of input during web page generation ('cross-site scripting') vulnerability in Wikimedia Foundation MediaWiki - WikiLambda extension allows Stored XSS.
This issue affects MediaWiki - WikiLambda extension: before 1.46.1.
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Analysis
by VulDB Data Team • 09/30/2026
The identified vulnerability represents a critical security flaw within the WikiLambda extension for the MediaWiki platform, specifically classified as an improper neutralization of input during web page generation, commonly known as cross-site scripting or XSS. This particular instance is categorized as a stored XSS vulnerability, which distinguishes it from reflected attacks by persisting on the target server rather than being transmitted solely through the browser request. The flaw exists in versions of the WikiLambda extension prior to version 1.46.1 and stems from insufficient validation and sanitization mechanisms when processing user-supplied input that is subsequently rendered into HTML content without proper encoding or escaping.
From a technical perspective, the vulnerability arises because the application fails to adequately sanitize special characters such as angle brackets, quotes, and ampersands within specific fields managed by WikiLambda. When an attacker injects malicious JavaScript code into these inputs, the server accepts this data and stores it in its database without triggering appropriate security checks. Subsequently, when other users or administrators access pages containing this stored payload, the browser interprets the injected script as legitimate content from the trusted domain. This execution context allows the malicious script to operate with the same privileges as any other script running on the page, effectively bypassing standard client-side protections like the Same-Origin Policy because the code originates from a trusted source in the eyes of the browser.
The operational impact of this stored XSS vulnerability is severe due to its persistent nature and potential for widespread exposure. Unlike reflected XSS attacks that require social engineering to trick a specific user into clicking a malicious link, stored XSS remains active on the server until manually removed by an administrator. This means that every user who views the compromised page becomes a potential victim of the attack without any additional interaction required beyond normal browsing behavior. An attacker can exploit this flaw to steal session cookies, hijack administrative accounts, deface web pages, or redirect users to malicious sites designed for phishing or malware distribution. In collaborative environments like Wikimedia projects, where multiple contributors interact with shared content, a single compromised entry point can lead to the compromise of numerous user sessions and potentially disrupt the integrity of the entire platform if an administrator account is targeted.
This vulnerability aligns directly with CWE-79, which defines Improper Neutralization of Input During Web Page Generation as Cross-site Scripting (XSS). Furthermore, from a threat intelligence perspective, this exploit technique maps to MITRE ATT&CK techniques such as T1059 Command and Scripting Interpreter for executing arbitrary code within the browser environment, and potentially T1204 User Execution if the attack relies on inducing users to interact with specific content. The persistence of the payload also relates to T1189 Drive-by Compromise or T1071 Application Layer Protocol depending on how the data is exfiltrated after execution.
To mitigate this vulnerability, organizations running MediaWiki with the WikiLambda extension must immediately upgrade to version 1.46.1 or later where these input handling issues have been addressed by the developers. In cases where immediate patching is not feasible due to operational constraints, administrators should implement strict Content Security Policy headers that restrict script execution sources and disable inline scripts if possible. Additionally, deploying a Web Application Firewall can provide an additional layer of defense by filtering out malicious payloads before they reach the application logic. Regular security audits focusing on input validation across all user-facing forms and data entry points are essential to prevent similar flaws from being introduced in future updates or custom extensions.