CVE-2019-16333 in GetSimple
Summary
by MITRE
GetSimple CMS v3.3.15 has Persistent Cross-Site Scripting (XSS) in admin/theme-edit.php.
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Analysis
by VulDB Data Team • 12/25/2023
The vulnerability identified as CVE-2019-16333 represents a critical persistent cross-site scripting flaw discovered in GetSimple CMS version 3.3.15 within the admin/theme-edit.php component. This vulnerability exposes the content management system to malicious script injection attacks that can persist across user sessions and affect multiple visitors. The issue occurs when administrative users interact with the theme editing functionality, where user-supplied input is not properly sanitized or validated before being rendered back to the browser. This persistent nature of the vulnerability means that malicious scripts injected through the theme editing interface will execute whenever any user accesses the affected pages, making it particularly dangerous for administrators and content creators who frequently use the administrative interface.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding practices within the theme-edit.php file. When administrators modify theme settings or upload custom theme elements, the system fails to properly escape or filter user-provided content before storing it in the database or rendering it in subsequent page requests. This allows attackers to inject malicious javascript payloads that can execute in the context of other users' browsers who view the affected theme settings. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws, and more precisely aligns with CWE-80 which deals with improper neutralization of script in different contexts. The attack vector is particularly concerning as it leverages the trust relationship between legitimate administrators and the CMS system, potentially allowing attackers to escalate privileges or steal session cookies.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with the capability to perform session hijacking, steal administrative credentials, and potentially gain full control over the CMS installation. An attacker who successfully exploits this vulnerability can execute malicious code in the context of any logged-in administrator's browser, potentially leading to complete system compromise. The persistent nature means that even after the initial injection, the malicious scripts will continue to execute for all users who view the affected theme pages, creating a long-term security risk. This vulnerability also aligns with ATT&CK technique T1059.007 which covers scripting through web shell execution, and T1566.001 which involves spearphishing attachments, as the persistent nature makes this a prime target for maintaining access and executing malicious payloads over extended periods.
Organizations using GetSimple CMS version 3.3.15 should immediately implement multiple layers of mitigation strategies to address this vulnerability. The primary recommendation involves updating to the latest version of GetSimple CMS where this vulnerability has been patched, as the developers have addressed the input validation and output encoding issues in subsequent releases. Additionally, administrators should implement strict input validation for all user-supplied data within the theme editing functionality, ensuring that any content submitted through the interface undergoes proper sanitization before being stored or rendered. Network-level protections including web application firewalls and content filtering systems can provide additional defense-in-depth measures to detect and block malicious script injection attempts. Regular security audits of administrative interfaces and input validation processes should be conducted to identify similar vulnerabilities in other parts of the CMS. Security monitoring should be implemented to detect unusual activity patterns that might indicate exploitation attempts, and access controls should be reviewed to ensure that only authorized personnel have administrative privileges in the theme editing components.