CVE-2023-29201 in xwiki-commons-xml
Summary
by MITRE • 04/15/2023
XWiki Commons are technical libraries common to several other top level XWiki projects. The "restricted" mode of the HTML cleaner in XWiki, introduced in version 4.2-milestone-1, only escaped `` and ``-tags but neither attributes that can be used to inject scripts nor other dangerous HTML tags like ``. As a consequence, any code relying on this "restricted" mode for security is vulnerable to JavaScript injection ("cross-site scripting"/XSS). When a privileged user with programming rights visits such a comment in XWiki, the malicious JavaScript code is executed in the context of the user session. This allows server-side code execution with programming rights, impacting the confidentiality, integrity and availability of the XWiki instance. This problem has been patched in XWiki 14.6 RC1 with the introduction of a filter with allowed HTML elements and attributes that is enabled in restricted mode. There are no known workarounds apart from upgrading to a version including the fix.
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Analysis
by VulDB Data Team • 04/30/2023
The vulnerability CVE-2023-29201 affects XWiki Commons, which serves as foundational technical libraries supporting multiple top-level XWiki projects. This security flaw resides in the HTML cleaner's "restricted" mode implementation that was introduced in version 4.2-milestone-1. The restricted mode was designed to sanitize HTML content by escaping certain dangerous tags but contained critical implementation gaps that rendered it ineffective against cross-site scripting attacks. The vulnerability specifically fails to properly filter attributes that could be exploited for script injection and does not adequately block other dangerous HTML elements beyond the basic tag escaping mechanism.
The technical flaw represents a classic insufficient input validation and output encoding issue, classified under CWE-79 - Cross-site Scripting. The HTML cleaner's restricted mode only escaped `<script>` and `</script>` tags while leaving other potentially dangerous attributes and elements unfiltered, creating an attack surface where malicious JavaScript code could be injected through user comments or content. When privileged users with programming rights access pages containing such malicious content, the injected JavaScript executes within the user's session context, effectively allowing attackers to leverage these elevated privileges. This creates a severe chain of compromise where an attacker can execute server-side code with full programming rights, directly impacting the fundamental security properties of confidentiality, integrity, and availability.
The operational impact of this vulnerability extends beyond simple XSS exploitation to encompass complete system compromise. An attacker who successfully injects malicious JavaScript code can perform actions equivalent to those performed by privileged users, potentially leading to unauthorized code execution, data exfiltration, system modification, and service disruption. The vulnerability affects the entire XWiki instance since the compromised user sessions with programming rights have extensive access to system resources and functionality. This type of vulnerability aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: JavaScript, where attackers leverage browser-based scripting capabilities to execute malicious code in the context of legitimate user sessions.
The security fix implemented in XWiki 14.6 RC1 addresses this vulnerability through the introduction of a comprehensive filter mechanism that explicitly defines allowed HTML elements and attributes when restricted mode is enabled. This approach follows the principle of whitelisting rather than blacklisting, which is considered a more secure methodology for input validation. The patch resolves the fundamental design flaw by ensuring that only safe HTML constructs are permitted in restricted mode, eliminating the possibility of script injection through attribute-based attacks or dangerous HTML elements. Organizations affected by this vulnerability should prioritize upgrading to version 14.6 RC1 or later, as no effective workarounds exist for this specific implementation gap in the HTML sanitization process. The vulnerability demonstrates the critical importance of proper HTML sanitization in web applications and the potential consequences of incomplete security implementations that appear to provide protection but contain fundamental flaws in their design.