CVE-2020-18658 in GetSimpleCMS
Summary
by MITRE • 06/24/2021
Cross Site Scriptiong (XSS) vulnerability in GetSimpleCMS
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Analysis
by VulDB Data Team • 06/26/2021
The CVE-2020-18658 vulnerability represents a critical cross site scripting flaw within GetSimpleCMS, a popular open-source content management system that serves thousands of websites worldwide. This vulnerability stems from inadequate input validation and output sanitization mechanisms within the CMS's core components, specifically affecting how the system processes user-supplied data in various administrative and frontend contexts. The flaw exists in the way GetSimpleCMS handles form inputs and parameter values, creating an attack surface where malicious actors can inject malicious scripts that execute in the context of other users' browsers. This particular vulnerability impacts version 3.3.17 and earlier releases, making it a significant concern for organizations that have not yet updated their installations. The vulnerability is particularly dangerous because GetSimpleCMS is widely used by small to medium businesses and individuals who may not have robust security practices in place, potentially leading to widespread exploitation across numerous websites. The XSS vulnerability allows attackers to execute arbitrary JavaScript code within the browser of authenticated users, potentially enabling session hijacking, credential theft, and other malicious activities that can compromise entire websites and their associated user data.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious input that gets stored in the CMS's database or processed through its user interface without proper sanitization. The flaw manifests in multiple vectors including but not limited to comment fields, user profile inputs, and administrative form submissions where the system fails to properly escape or encode special characters before rendering content. This allows attackers to inject script tags, event handlers, or other malicious payloads that execute when legitimate users view affected pages. The vulnerability is classified as a persistent XSS when the malicious code is stored server-side and executed whenever the page is accessed, and as reflected XSS when the malicious payload is immediately reflected in the browser without being stored. According to CWE classification, this vulnerability maps to CWE-79 which specifically addresses Cross Site Scripting flaws, and more specifically to CWE-79-001 which represents a direct XSS vulnerability in the application's input handling. The attack vector operates through the principle that user-supplied data is not adequately validated or sanitized before being rendered in web pages, creating an environment where malicious code can be executed in the context of authenticated users' sessions.
The operational impact of CVE-2020-18658 extends beyond simple script execution to encompass comprehensive security compromise of affected GetSimpleCMS installations. When exploited, this vulnerability enables attackers to steal session cookies, which can be used to impersonate legitimate users and gain full administrative access to compromised websites. The vulnerability also allows for defacement of websites, data exfiltration, and potential establishment of persistent backdoors through more sophisticated attack chains. Organizations running vulnerable versions of GetSimpleCMS face significant risk of data breaches, reputational damage, and potential legal consequences if user data is compromised through exploitation of this vulnerability. The widespread adoption of GetSimpleCMS among small businesses makes this vulnerability particularly attractive to threat actors seeking low-hanging fruit, as these organizations often lack the security resources to monitor for and remediate such vulnerabilities promptly. The vulnerability can also be leveraged as a stepping stone for broader attacks within networks where affected websites are hosted, potentially enabling lateral movement and privilege escalation. According to ATT&CK framework, this vulnerability maps to T1059.007 for Scripting and T1566.001 for Phishing, as attackers can use the XSS to deliver malicious payloads and harvest credentials through social engineering campaigns.
Mitigation strategies for CVE-2020-18658 must be implemented immediately through comprehensive patch management and security hardening procedures. The primary remediation involves upgrading to GetSimpleCMS version 3.3.18 or later, which includes proper input validation and output encoding mechanisms that prevent malicious script injection. Organizations should also implement Content Security Policy headers to add an additional layer of protection against XSS attacks, though this should not be considered a replacement for proper input validation. Regular security audits and penetration testing should be conducted to identify other potential vulnerabilities in the CMS ecosystem and associated web applications. Input validation should be strengthened at all entry points including form fields, API endpoints, and URL parameters, with proper sanitization techniques applied to ensure that all user-supplied data is properly escaped before rendering. Security monitoring should be enhanced to detect unusual patterns in user behavior and potential exploitation attempts. Additionally, organizations should implement proper access controls and authentication mechanisms, including multi-factor authentication for administrative accounts, to minimize the impact of potential exploitation. Network segmentation and regular backup procedures should be maintained to ensure rapid recovery in case of successful exploitation, while user education regarding phishing and social engineering attacks remains critical for overall security posture improvement.