CVE-2020-36415 in CMS Made Simple
Summary
by MITRE • 07/03/2021
A stored cross scripting (XSS) vulnerability in CMS Made Simple 2.2.14 allows authenticated attackers to execute arbitrary web scripts or HTML via a crafted payload entered into the "Create a new Stylesheet" parameter under the "Stylesheets" module.
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Analysis
by VulDB Data Team • 07/09/2021
This vulnerability represents a critical stored cross-site scripting flaw in CMS Made Simple version 2.2.14 that enables authenticated attackers to inject malicious code into the application's stylesheet functionality. The vulnerability exists within the "Create a new Stylesheet" parameter of the "Stylesheets" module, where user input is not properly sanitized or validated before being stored and subsequently rendered in the web interface. When an attacker successfully exploits this weakness, they can execute arbitrary web scripts or HTML code within the context of other users' browsers who view the affected stylesheet content. This stored XSS vulnerability poses significant risks as it allows attackers to persistently inject malicious payloads that can compromise user sessions, steal sensitive information, or redirect users to malicious websites. The vulnerability is particularly concerning because it requires only authentication to the CMS system, meaning that any user with valid credentials can exploit this flaw. According to CWE standards, this represents a CWE-79: Improper Neutralization of Input During Web Page Generation, which specifically addresses the failure to properly sanitize user-controllable data before incorporating it into web pages. The attack vector aligns with ATT&CK technique T1566.001: Phishing, as attackers can leverage this vulnerability to create malicious stylesheet content that can be used in social engineering campaigns. The operational impact extends beyond simple script execution, as attackers can manipulate the victim's browser environment to perform actions such as stealing session cookies, modifying page content, or conducting further attacks through the compromised user context. The vulnerability demonstrates a fundamental flaw in input validation and output encoding practices within the CMS application's stylesheet management functionality.
The technical exploitation of this vulnerability requires an attacker to have valid authentication credentials within the CMS system, which significantly reduces the attack surface compared to unauthenticated vulnerabilities. However, this also means that even low-privilege users can potentially escalate their access through this vector, particularly if they can influence content that other users will view. The stored nature of the vulnerability means that the malicious payload persists in the database and will be executed each time the affected stylesheet is rendered, making it particularly dangerous for long-term compromise. The vulnerability's impact is amplified when considering that stylesheet content often serves as a foundational element in website presentation, making it likely that users will regularly view affected content. Security researchers have noted that this class of vulnerability often indicates broader issues with the application's data sanitization practices, suggesting that similar weaknesses may exist in other input handling areas. The vulnerability's classification under CWE-79 highlights the importance of implementing proper input validation and output encoding mechanisms to prevent malicious data from being interpreted as executable code. In enterprise environments where CMS Made Simple is used for content management, this vulnerability can serve as a stepping stone for attackers to gain deeper access to systems and potentially compromise the entire web infrastructure.
Organizations using CMS Made Simple 2.2.14 should immediately implement mitigations to address this stored XSS vulnerability. The primary remediation involves upgrading to a patched version of the CMS Made Simple software where the input validation has been properly strengthened for stylesheet creation parameters. System administrators should also implement additional defensive measures such as input sanitization at multiple layers, including web application firewalls that can detect and block malicious payloads in stylesheet creation requests. Regular security audits should be conducted to identify similar input handling vulnerabilities across the application's functionality, particularly in areas where user-generated content is processed and stored. The implementation of content security policies can provide additional protection by limiting the execution of unauthorized scripts within the application's context. Monitoring and logging of stylesheet creation activities should be enhanced to detect anomalous behavior that might indicate exploitation attempts. Security teams should also consider implementing privilege separation and least-privilege principles to minimize the potential impact of compromised accounts. Regular vulnerability assessments and penetration testing should be conducted to ensure that similar weaknesses do not exist in other modules or components of the CMS system. The vulnerability serves as a reminder of the critical importance of proper input validation and output encoding in web applications, particularly in content management systems where user input is frequently processed and rendered in web contexts. Organizations should also review their incident response procedures to ensure they can quickly detect and remediate such vulnerabilities when they are discovered in their systems.