CVE-2018-9861 in Enhanced Image Plugin
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Enhanced Image (aka image2) plugin for CKEditor (in versions 4.5.10 through 4.9.1; fixed in 4.9.2), as used in Drupal 8 before 8.4.7 and 8.5.x before 8.5.2 and other products, allows remote attackers to inject arbitrary web script through a crafted IMG element.
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Analysis
by VulDB Data Team • 03/03/2023
The CVE-2018-9861 vulnerability represents a critical cross-site scripting flaw within the Enhanced Image plugin of CKEditor, affecting a wide range of applications including Drupal 8 versions prior to 8.4.7 and 8.5.x prior to 8.5.2. This vulnerability resides in the image2 plugin's handling of image elements, specifically when processing crafted IMG tags that contain malicious script code. The flaw enables remote attackers to execute arbitrary web scripts within the context of a victim's browser, potentially leading to session hijacking, data theft, or complete compromise of user sessions. The vulnerability affects CKEditor versions from 4.5.10 through 4.9.1, making it particularly concerning given the widespread adoption of CKEditor in content management systems and web applications.
The technical exploitation of this vulnerability occurs through the improper sanitization of IMG element attributes within the Enhanced Image plugin's processing pipeline. When CKEditor renders images, it fails to adequately validate or escape user-supplied attributes such as src, alt, or other HTML attributes that can contain malicious JavaScript code. This processing flaw allows attackers to inject script tags or other malicious content that executes when the rendered page is viewed by authenticated users. The vulnerability specifically manifests when the editor processes image elements that contain crafted attributes, bypassing standard input validation mechanisms that should prevent such malicious content from being stored or executed. This weakness aligns with CWE-79, which describes cross-site scripting vulnerabilities resulting from insufficient input validation and output encoding.
The operational impact of CVE-2018-9861 extends beyond simple script execution, potentially enabling attackers to perform session hijacking, steal sensitive user information, or redirect users to malicious websites. In Drupal environments, this vulnerability could allow attackers to gain elevated privileges if they can compromise administrative accounts through session manipulation or credential theft. The vulnerability's exploitation requires minimal user interaction, typically involving a simple page load or content viewing action, making it particularly dangerous in environments where users frequently interact with rich text content. Attackers can leverage this vulnerability to establish persistent access to user sessions, potentially leading to complete system compromise. The vulnerability also aligns with ATT&CK technique T1059.001, which covers command and scripting interpreter usage, specifically targeting web-based scripting environments.
Organizations should implement immediate mitigations including updating to CKEditor version 4.9.2 or later, which contains the necessary patches to address the XSS vulnerability. Additionally, administrators should review and strengthen input validation mechanisms within their content management systems, implementing proper HTML sanitization and attribute validation for all user-generated content. The remediation process should include thorough testing of updated systems to ensure that the patch does not introduce regressions in functionality while maintaining the security improvements. Organizations should also consider implementing content security policies to add an additional layer of protection against XSS attacks, as outlined in the OWASP XSS Prevention Cheat Sheet. Regular security assessments and vulnerability scanning should be conducted to identify similar vulnerabilities in other components of the web application stack, particularly within rich text editors and content rendering systems that process user input.