CVE-2019-9554 in Craft
Summary
by MITRE
In the 3.1.12 Pro version of Craft CMS, XSS has been discovered in the header insertion field when adding source code at an s/admin/entries/news/new URI.
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Analysis
by VulDB Data Team • 08/17/2025
The vulnerability identified as CVE-2019-9554 represents a cross-site scripting flaw within Craft CMS version 3.1.12 Pro that specifically affects the administrative interface. This issue manifests in the header insertion field when users attempt to add source code through the administrative entry creation endpoint at s/admin/entries/news/new. The vulnerability stems from insufficient input validation and output sanitization mechanisms within the content management system's administrative components. Attackers can exploit this weakness by injecting malicious javascript code into the header insertion field, which then executes in the context of other users' browsers who view the affected content. The attack vector is particularly concerning because it targets the administrative interface where privileged users typically perform content management tasks, potentially allowing for privilege escalation or unauthorized access to sensitive system functions.
The technical implementation of this vulnerability aligns with CWE-79 Cross-site Scripting flaws, specifically categorized as reflected XSS in the context of administrative interfaces. The flaw occurs due to improper sanitization of user-supplied input before rendering it within the web application's response. When administrators navigate to the entry creation page and input malicious code into the header insertion field, the system fails to properly encode or escape the content before storing or displaying it. This allows attackers to craft payloads that can execute in the browser context of authenticated users, potentially leading to session hijacking, data exfiltration, or further exploitation of the compromised administrative session. The vulnerability demonstrates a classic failure in the principle of least privilege where administrative functions lack proper input validation controls.
The operational impact of CVE-2019-9554 extends beyond simple script execution, as it can be leveraged for more sophisticated attacks within the Craft CMS environment. An attacker who successfully exploits this vulnerability can potentially escalate privileges, access sensitive administrative functions, or steal session cookies from authenticated administrators. The attack requires minimal user interaction since the exploitation occurs during normal content creation workflows, making it particularly dangerous in environments where administrators frequently create or modify content. The vulnerability also represents a significant risk to the integrity of the content management system, as it allows for persistent malicious code injection that could affect multiple users over time. Organizations relying on Craft CMS for content management are particularly vulnerable since this flaw impacts the core administrative functionality where users have elevated privileges and access to system resources.
Mitigation strategies for CVE-2019-9554 should prioritize immediate patching of the Craft CMS instance to version 3.1.13 or later, which contains the necessary security fixes. Organizations should implement additional defensive measures including input validation at multiple layers, output encoding for all user-supplied content, and regular security audits of administrative interfaces. The implementation of content security policies can help prevent execution of unauthorized scripts even if an attacker manages to inject malicious code. Network segmentation and privileged access controls should be enforced to limit the potential damage from successful exploitation attempts. Regular security training for administrators can help prevent social engineering attacks that might exploit this vulnerability, while monitoring systems should be implemented to detect unusual administrative activities that could indicate exploitation attempts. The vulnerability also highlights the importance of maintaining current security practices and adhering to the principle of defense in depth as outlined in various cybersecurity frameworks including those recommended by nist and iso 27001 standards.