CVE-2018-16358 in DotClear
Summary
by MITRE
A cross-site scripting (XSS) vulnerability in inc/core/class.dc.core.php in the media manager in Dotclear through 2.14.1 allows remote authenticated users to upload HTML content containing an XSS payload with the file extension .ahtml.
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Analysis
by VulDB Data Team • 03/20/2020
The vulnerability identified as CVE-2018-16358 represents a critical cross-site scripting flaw within the Dotclear content management system version 2.14.1 and earlier. This issue resides in the core media manager functionality, specifically within the inc/core/class.dc.core.php file, where the system fails to properly sanitize user-uploaded content. The vulnerability affects authenticated users who possess the necessary permissions to upload media files, creating a pathway for malicious actors to execute persistent XSS attacks against other users of the platform.
The technical exploitation of this vulnerability occurs through a carefully crafted file upload process that leverages the .ahtml file extension. This specific file extension appears to bypass normal content validation checks that would typically prevent HTML uploads, allowing attackers to embed malicious JavaScript payloads within what appears to be a legitimate media file. The .ahtml extension essentially acts as a backdoor mechanism that circumvents the system's security controls, enabling the execution of malicious code when the uploaded file is subsequently viewed or processed by other users. This flaw demonstrates a significant weakness in the application's input validation and file type handling mechanisms.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with persistent access to victim sessions and potentially full system compromise. When authenticated users view or interact with the maliciously uploaded content, the embedded XSS payload executes in their browser context, enabling various attack vectors including session hijacking, credential theft, redirection to malicious sites, and data exfiltration. The vulnerability's persistence stems from the fact that the malicious content is stored server-side and executed whenever the file is accessed, making it particularly dangerous in multi-user environments where administrators and regular contributors may encounter the payload during routine operations.
Organizations utilizing Dotclear systems face substantial risk from this vulnerability, as it can be exploited by attackers with minimal privileges to gain elevated access to the application's functionality. The attack requires only authenticated access to the media manager, which is often granted to content editors and administrators. This makes the vulnerability particularly concerning for sites with multiple users or those that do not enforce strict access controls. The vulnerability also aligns with CWE-79, which specifically addresses cross-site scripting flaws, and could be categorized under ATT&CK technique T1059.007 for JavaScript execution within web applications. Security practitioners should note that this vulnerability represents a classic case of insufficient input sanitization, where file type validation is bypassed through the use of non-standard extensions.
Mitigation strategies for this vulnerability should focus on immediate patching of affected Dotclear installations to version 2.14.2 or later, where the issue has been resolved through enhanced file validation and sanitization. Additionally, administrators should implement strict file type restrictions that prevent upload of files with potentially dangerous extensions, even when they appear to be legitimate media files. Network-level controls such as web application firewalls can provide additional protection by detecting and blocking suspicious file upload patterns. The security posture should include regular security audits of file upload mechanisms, implementation of content security policies to prevent script execution, and user education regarding the risks of viewing untrusted media content. Organizations should also consider implementing automated scanning tools that can detect and prevent the upload of malicious files with embedded XSS payloads.