CVE-2025-46558: XWiki Markdown Syntax XSS Vulnerability

CVE-2025-46558 Overview

CVE-2025-46558 is a critical Cross-Site Scripting (XSS) vulnerability affecting XWiki Contrib's Syntax Markdown extension. This extension allows importing Markdown content into wiki pages and creating wiki content in Markdown. In versions starting from 8.2 to before 8.9, the Markdown syntax parser is vulnerable to XSS through improperly sanitized HTML content. Any user can embed malicious JavaScript code within Markdown content that will execute in the browser of any other user visiting the affected document or comment.

Critical Impact

When exploited by or against a user with administrative or programming rights, this vulnerability compromises the confidentiality, integrity, and availability of the entire XWiki installation, potentially allowing complete takeover of the wiki platform.

Affected Products

• XWiki Syntax Markdown versions 8.2 through 8.8.x
• XWiki installations using the syntax-markdown-commonmark12 component
• XWiki wiki pages and comments utilizing Markdown syntax

Discovery Timeline

• April 30, 2025 - CVE-2025-46558 published to NVD
• August 26, 2025 - Last updated in NVD database

Technical Details for CVE-2025-46558

Vulnerability Analysis

This vulnerability exists in the Markdown parsing implementation within XWiki's Syntax Markdown extension. The core issue stems from insufficient sanitization of HTML content embedded within Markdown syntax. The Markdown parser processes user-supplied content and converts it to HTML for rendering, but fails to properly escape or filter potentially dangerous JavaScript code embedded within HTML tags.

The vulnerability is particularly severe because XWiki allows users with varying privilege levels to create and edit wiki content. When a privileged administrator views a page or comment containing the malicious payload, the JavaScript executes within their authenticated session context, potentially allowing session hijacking, privilege escalation, or arbitrary actions performed on behalf of the administrator.

The attack requires network access and user interaction (the victim must view the malicious content), but the low attack complexity and low privileges required for exploitation make this a significant threat to XWiki deployments.

Root Cause

The root cause is improper input validation and output encoding in the Markdown-to-HTML conversion process (CWE-79). The Syntax Markdown extension failed to properly sanitize HTML content embedded within Markdown documents before rendering, allowing arbitrary JavaScript injection. The vulnerability exists in the AbstractMarkdownConfiguration.java file where parser extensions are configured without adequate HTML filtering.

Attack Vector

The attack vector is network-based, requiring an authenticated attacker with low privileges to inject malicious JavaScript code into wiki pages or comments using Markdown syntax. The attack flow involves:

1. Attacker creates or edits a wiki page/comment using Markdown syntax
2. Malicious JavaScript is embedded within HTML tags in the Markdown content
3. Victim user (potentially an administrator) views the page or comment
4. The malicious script executes in the victim's browser context
5. If the victim has administrative privileges, the attacker gains access to sensitive operations

// Security patch in AbstractMarkdownConfiguration.java
// Source: https://github.com/xwiki-contrib/syntax-markdown/commit/d136472d6e8a47981a0ede420a9096f88ffa5035

                getLogger().warn("Invalid extension: [{}]. Root cause: [{}]", extensionClass.getName(),
                    ExceptionUtils.getRootCauseMessage(e));
            }
-            options.set(Parser.EXTENSIONS, extensions);
        }
+        options.set(Parser.EXTENSIONS, extensions);

        return options;
    }

The patch modifies the parser extension configuration to ensure proper handling of HTML content within Markdown. Additionally, the test dependencies were updated to include the xwiki-rendering-macro-html component for comprehensive security testing:

// Security patch in pom.xml adding HTML macro test dependency
// Source: https://github.com/xwiki-contrib/syntax-markdown/commit/d136472d6e8a47981a0ede420a9096f88ffa5035

       <version>${rendering.version}</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.xwiki.rendering</groupId>
+      <artifactId>xwiki-rendering-macro-html</artifactId>
+      <version>${rendering.version}</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
   <build>
     <plugins>

Detection Methods for CVE-2025-46558

Indicators of Compromise

• Unusual JavaScript code embedded within wiki page content or comments using Markdown syntax
• Wiki pages containing HTML <script> tags or JavaScript event handlers (e.g., onerror, onload) within Markdown content
• Unexpected administrative actions or configuration changes following user viewing of wiki content
• Browser console errors or unexpected network requests when viewing wiki pages

Detection Strategies

• Implement content security policy (CSP) headers to detect and block inline script execution
• Monitor wiki page edit logs for suspicious Markdown content containing HTML script tags
• Review recent page edits and comments for embedded JavaScript patterns such as <script>, javascript:, or event handler attributes
• Deploy web application firewalls (WAF) with XSS detection rules targeting wiki content endpoints

Monitoring Recommendations

• Enable detailed audit logging for all wiki page and comment modifications
• Monitor for unusual patterns in wiki content containing HTML within Markdown syntax
• Set up alerts for administrative actions performed immediately after page views
• Track browser-side errors and blocked script executions via CSP violation reports

How to Mitigate CVE-2025-46558

Immediate Actions Required

• Upgrade XWiki Syntax Markdown extension to version 8.9 or later immediately
• Review all existing wiki pages and comments for potentially malicious embedded JavaScript
• Temporarily restrict wiki editing capabilities to trusted users until the patch is applied
• Implement Content Security Policy headers to mitigate XSS impact

Patch Information

XWiki has released version 8.9 of the Syntax Markdown extension which addresses this vulnerability. The security fix is available via commit d136472d6e8a47981a0ede420a9096f88ffa5035 and resolves the HTML sanitization issue in the Markdown parser. Organizations should update to version 8.9 or later as soon as possible.

For detailed patch information, refer to the GitHub Security Advisory GHSA-8g2j-rhfh-hq3r and the XWiki JIRA Issue MARKDOWN-80.

Workarounds

• Disable the Markdown syntax extension entirely until the patch can be applied
• Restrict wiki page and comment creation/editing to trusted administrators only
• Deploy a web application firewall with rules to filter JavaScript in Markdown content
• Implement strict Content Security Policy headers to prevent inline script execution

# Configuration example - Add CSP headers to XWiki web server
# For Apache HTTP Server, add to httpd.conf or .htaccess:
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none';"

# For Nginx, add to server block:
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none';";