CVE-2015-6737 in Widgets Extension
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Widgets extension for MediaWiki allows remote attackers to inject arbitrary web script or HTML via vectors involving base64 encoded content.
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Analysis
by VulDB Data Team • 06/14/2022
The CVE-2015-6737 vulnerability represents a critical cross-site scripting flaw within the Widgets extension for MediaWiki, a widely deployed wiki software platform used by organizations ranging from small businesses to large enterprises including Wikimedia Foundation. This vulnerability specifically affects versions of MediaWiki prior to 1.25.1 and 1.26.1, creating a significant security risk for wiki administrators who rely on the Widgets extension for dynamic content management and user interface customization. The flaw stems from insufficient input validation and sanitization mechanisms within the extension's handling of base64 encoded content, which is commonly used for embedding various types of media and widgets within wiki pages.
The technical implementation of this vulnerability occurs when the Widgets extension processes base64 encoded content without proper sanitization of the decoded data. Attackers can craft malicious base64 encoded payloads that, when processed by the extension, execute arbitrary JavaScript code within the context of other users' browsers. This occurs because the extension fails to properly validate or escape the decoded content before rendering it in the browser, allowing attackers to inject malicious scripts that can steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users. The vulnerability specifically leverages the base64 encoding mechanism as an attack vector, making it particularly insidious since it can bypass traditional input filtering mechanisms that might not inspect base64 decoded content.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform sophisticated attacks such as session hijacking, credential theft, and data exfiltration from wiki environments. When exploited, the vulnerability allows remote attackers to execute arbitrary code in the context of other users' browsers, potentially leading to complete compromise of user accounts and unauthorized access to sensitive wiki content. Organizations relying on MediaWiki for collaborative workspaces, documentation systems, or internal knowledge bases face significant risk, as the vulnerability can be exploited through various means including editing wiki pages, submitting comments, or manipulating widget configurations. The attack surface is particularly broad given that MediaWiki is used in enterprise environments where users may have elevated privileges, making the potential impact of exploitation particularly severe.
Security mitigations for this vulnerability primarily involve immediate patching of affected MediaWiki installations to versions 1.25.1 or 1.26.1, which contain the necessary fixes for proper input sanitization. Administrators should also implement additional defensive measures including content security policy headers, input validation at multiple layers, and monitoring for suspicious widget content. The vulnerability aligns with CWE-79 Cross-site Scripting and maps to ATT&CK technique T1059.007 for script execution, with the base64 encoding serving as a means to evade detection and bypass traditional security controls. Organizations should conduct thorough security assessments of their MediaWiki installations, review widget configurations, and implement proper access controls to minimize the risk of exploitation. The vulnerability underscores the importance of proper input validation and output encoding in web applications, particularly in content management systems where user-generated content processing is common.