CVE-2010-4183 in Htmlpurifier
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in HTML Purifier before 4.1.0, when Internet Explorer is used, allow remote attackers to inject arbitrary web script or HTML via a crafted (1) background-image, (2) background, or (3) font-family Cascading Style Sheets (CSS) property, a different vulnerability than CVE-2010-2479.
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Analysis
by VulDB Data Team • 02/08/2019
The vulnerability described in CVE-2010-4183 represents a significant security flaw in the HTML Purifier library version 4.0.0 and earlier, specifically affecting users of Internet Explorer browsers. This issue falls under the category of cross-site scripting vulnerabilities that can be exploited by remote attackers to inject malicious code into web applications. The flaw manifests when HTML Purifier processes CSS properties in a manner that fails to properly sanitize or escape user-supplied content, creating an attack surface that can be leveraged for various malicious activities.
The technical implementation of this vulnerability occurs through the improper handling of three specific CSS properties: background-image, background, and font-family. When these properties are processed by HTML Purifier versions prior to 4.1.0, the sanitization mechanism fails to adequately filter or escape potentially malicious content contained within these CSS attributes. This failure allows attackers to craft specially designed CSS code that contains embedded JavaScript or HTML fragments, which can then be executed when the compromised content is rendered in Internet Explorer browsers. The vulnerability is particularly concerning because it specifically targets Internet Explorer's rendering engine, which has historically been more susceptible to certain types of CSS-based attacks compared to other browsers.
The operational impact of this vulnerability extends beyond simple XSS exploitation, as it enables attackers to perform a range of malicious activities including session hijacking, credential theft, and redirection to malicious websites. When Internet Explorer users encounter content containing malicious CSS properties, the browser's rendering engine executes the embedded scripts, potentially compromising the user's session and exposing sensitive data. The vulnerability's classification as a CWE-79 (Cross-site Scripting) issue demonstrates its fundamental nature as a weakness in input handling and output encoding, while its specific targeting of CSS properties aligns with ATT&CK technique T1211 (Exploitation for Defense Evasion) and T1566 (Phishing). The fact that this vulnerability differs from CVE-2010-2479 indicates that it represents a distinct code path or implementation flaw within the HTML Purifier library's CSS sanitization routines.
Organizations using HTML Purifier in their web applications face significant risk from this vulnerability, particularly those with user-generated content features or content management systems that rely on HTML filtering. The remediation approach requires immediate upgrading to HTML Purifier version 4.1.0 or later, which contains the necessary patches to properly sanitize CSS properties. Additionally, system administrators should implement comprehensive input validation and output encoding strategies, while also considering the use of Content Security Policy headers as an additional defense layer. The vulnerability highlights the importance of thorough testing across different browser environments and underscores the necessity of maintaining up-to-date security libraries to prevent exploitation of known vulnerabilities.