CVE-2026-104461 in YesWiki
Summary
by MITRE • 10/02/2026
YesWiki before 4.6.7 contains a stored cross-site scripting vulnerability in the Bazar FileField, which validates only the upload's file extension and never calls HtmlPurifierService::cleanFile, so SVG files are stored verbatim and served inline as image/svg+xml. Authenticated users can submit entries via POST /api/entries/{formId} with SVG files containing script that executes in the wiki origin when the file is opened, enabling administrator session or account compromise.
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Analysis
by VulDB Data Team • 10/02/2026
The vulnerability identified in YesWiki versions prior to 4.6.7 represents a critical stored cross-site scripting flaw located within the Bazar FileField component. This security defect stems from an insufficient validation mechanism during the file upload process. Specifically, the application relies exclusively on client-side or server-side checks of the uploaded file's extension rather than performing deep content inspection or sanitization. Consequently, when users submit SVG files through the API endpoint POST /api/entries/{formId}, the system accepts these inputs without invoking HtmlPurifierService::cleanFile, which is the designated service for stripping malicious code from HTML and XML-based formats. This architectural oversight allows attackers to store arbitrary JavaScript payloads directly within the wiki's storage infrastructure by embedding them inside SVG elements that are technically valid but contain executable script tags or event handlers.
From a technical perspective, the core issue lies in the misconfiguration of content type handling and sanitization workflows. Because SVG files are served inline with the MIME type image/svg+xml, modern web browsers interpret any embedded JavaScript as part of the document's execution context rather than treating it as static media data. This behavior transforms what should be a passive image resource into an active vector for code execution. The vulnerability is particularly severe because it does not require complex exploitation techniques; simply uploading a crafted SVG file containing malicious scripts is sufficient to plant persistent attack vectors within the application environment. These payloads remain stored on the server and are executed whenever another user, including administrators with elevated privileges, accesses or views the entry associated with the uploaded file.
The operational impact of this vulnerability extends beyond simple defacement or minor session hijacking for low-privileged users. Since authenticated users can trigger the execution of arbitrary JavaScript in the context of the wiki's origin, attackers can perform a wide range of malicious actions. These include stealing administrative cookies to seize control of administrator accounts, manipulating page content, exfiltrating sensitive data from other users' sessions, or performing unauthorized API calls on behalf of victims. The persistence of stored XSS means that even if the initial attacker is logged out, subsequent visits by privileged users will continue to trigger the malicious script, leading to repeated compromise events without further action required by the adversary. This significantly lowers the barrier for entry and increases the likelihood of successful exploitation against high-value targets within the organization.
In terms of industry classification standards, this vulnerability aligns with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting (XSS). More specifically, it falls under Stored XSS where malicious scripts are permanently stored on target servers and delivered to victims when they request data. From a tactical standpoint within the MITRE ATT&CK framework, this behavior corresponds to T1059 Command and Control via Application Layer Protocol for initial access or persistence mechanisms, as well as T1213 Data from Information Repositories if sensitive information is exfiltrated through the compromised session. The attack vector leverages valid application functionality (file upload) to bypass security controls, highlighting a failure in input validation logic that treats file extensions as sufficient proof of safety rather than inspecting actual content structure and code integrity.
To mitigate this vulnerability, immediate patching to YesWiki version 4.6.7 or later is required, as the developers have addressed the sanitization gap by ensuring proper cleaning routines are applied to all uploaded files regardless of extension. In environments where upgrading is not immediately feasible, administrators should implement strict allow-lists for file uploads that explicitly block SVG extensions if they are not strictly necessary for business operations. Additionally, configuring Content Security Policy headers can help mitigate the impact by restricting script execution sources and preventing inline scripts from running even if injected into DOM elements. Web Application Firewalls may also be configured to detect and block requests containing suspicious patterns within uploaded file contents or API payloads targeting the Bazar FileField endpoint. Regular security audits of file upload mechanisms should prioritize verifying that sanitization services are consistently invoked for all supported MIME types, particularly those capable of embedding executable code such as SVG, HTML, and XML variants.