CVE-2018-20418 in Craft
Summary
by MITRE
index.php?p=admin/actions/entries/save-entry in Craft CMS 3.0.25 allows XSS by saving a new title from the console tab.
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Analysis
by VulDB Data Team • 04/07/2025
The vulnerability identified as CVE-2018-20418 affects Craft CMS version 3.0.25 and represents a cross-site scripting flaw within the administrative console functionality. This issue specifically manifests when users attempt to save a new entry title through the console tab interface, creating a potential attack vector for malicious actors to execute unauthorized scripts in the context of authenticated admin sessions. The vulnerability resides in the index.php file within the admin actions entries save-entry endpoint, indicating a critical weakness in the input sanitization and output encoding mechanisms of the content management platform.
The technical exploitation of this vulnerability occurs through the manipulation of entry titles within the console tab functionality, where the application fails to properly sanitize user-supplied input before rendering it back to the browser. This failure in input validation creates an environment where malicious JavaScript code can be injected and subsequently executed when other administrators view the affected entries. The flaw essentially allows attackers to bypass the application's security controls by leveraging the trusted relationship between the admin user and the CMS interface, enabling the execution of arbitrary code within the victim's browser context. This type of vulnerability aligns with CWE-79, which specifically addresses cross-site scripting issues arising from insufficient input validation and output encoding.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the capability to escalate privileges and potentially gain full administrative control over the CMS instance. An attacker who successfully exploits this vulnerability can manipulate content, modify user permissions, access sensitive data, and potentially use the compromised admin session to pivot to other systems within the network. The attack requires minimal privileges since it targets the administrative console, making it particularly dangerous for organizations that rely heavily on Craft CMS for content management. This vulnerability also enables the exploitation of the ATT&CK technique T1059.007, which involves executing code through script-based attacks, and can contribute to broader attack chains involving credential theft and lateral movement.
Mitigation strategies for CVE-2018-20418 should include immediate patching of the Craft CMS instance to version 3.0.26 or later, which contains the necessary fixes for the input sanitization issues. Organizations should also implement additional defensive measures such as input validation at multiple layers, output encoding for all dynamic content, and regular security audits of administrative interfaces. Network segmentation and monitoring of admin console activities can help detect suspicious behavior patterns that may indicate exploitation attempts. The implementation of Content Security Policy headers and regular security training for administrators can further reduce the risk surface. Additionally, organizations should consider implementing web application firewalls to detect and block malicious input patterns that could be used to exploit similar vulnerabilities in other parts of their CMS infrastructure.