CVE-2020-37256 in Grav
Summary
by MITRE • 06/26/2026
Grav before 1.6.30 contains a cross-site scripting vulnerability in the Admin plugin page editor default security configuration. Privileged users with page editing capabilities can inject malicious scripts to execute arbitrary code and install malicious plugins for system access.
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Analysis
by VulDB Data Team • 06/26/2026
The vulnerability under discussion affects Grav versions prior to 1.6.30 and specifically targets the Admin plugin's page editor component through a cross-site scripting flaw in its default security configuration. This represents a critical weakness that enables authenticated attackers with page editing privileges to execute malicious code within the context of the application. The issue stems from insufficient input validation and output encoding mechanisms within the admin interface, allowing attackers to inject crafted scripts that persist in the system's content management structure. The vulnerability operates at the application layer and directly impacts the integrity and confidentiality of the Grav CMS environment.
The technical implementation of this XSS vulnerability occurs through the default security configuration of the Admin plugin's page editor functionality. When privileged users with editing capabilities create or modify pages, the system fails to properly sanitize user input before rendering it in the web interface. This creates an opportunity for attackers to inject malicious script payloads that execute in the context of other users' browsers who view the compromised pages. The vulnerability is particularly dangerous because it allows attackers to escalate privileges beyond simple script execution to full system compromise through plugin installation capabilities. The attack vector typically involves crafting malicious content within page editor fields that get rendered without proper sanitization, enabling persistent XSS attacks against authenticated users.
The operational impact of this vulnerability extends far beyond simple script injection as it provides attackers with a pathway to complete system compromise. Once an attacker successfully injects malicious scripts, they can leverage the elevated privileges associated with admin accounts to install malicious plugins, modify core application files, and potentially access sensitive data stored within the Grav system. This vulnerability directly relates to CWE-79 which defines Cross-Site Scripting vulnerabilities as a result of insufficient input validation. The attack chain follows patterns consistent with ATT&CK technique T1566.001 for initial access through malicious content and T1059.001 for execution of malicious code within the target environment, making it a significant threat to Grav installations.
Mitigation strategies for this vulnerability require immediate implementation of security updates to Grav version 1.6.30 or later where the XSS protections have been properly implemented. Organizations should enforce strict input validation and output encoding measures throughout the admin plugin interface, particularly in page editor components that handle user-generated content. Security administrators must review and harden default configurations to ensure that all user inputs undergo proper sanitization before being stored or rendered. Additionally implementing Content Security Policy headers can provide additional protection layers against XSS exploitation attempts. Regular security audits of CMS plugins and themes should be conducted to identify potential similar vulnerabilities, while privileged account monitoring should be enhanced to detect suspicious activities that may indicate exploitation attempts. The remediation process must also include comprehensive user education regarding safe content management practices and the importance of keeping CMS installations updated with latest security patches.