CVE-2020-36413 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 "Exclude these IP addresses from the "Site Down" status" parameter under the "Maintenance Mode" module.
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Analysis
by VulDB Data Team • 07/09/2021
This vulnerability exists within CMS Made Simple version 2.2.14 and represents a critical stored cross-site scripting flaw that can be exploited by authenticated attackers. The vulnerability specifically targets the Maintenance Mode module where administrators can configure IP address exclusions for site down status. When an attacker with valid credentials submits malicious input into the "Exclude these IP addresses from the Site Down" parameter, the application fails to properly sanitize or escape the input before storing it in the database. This stored payload is then executed whenever the affected page is rendered to users, creating a persistent XSS vector that can affect any visitor to the site.
The technical implementation of this vulnerability stems from inadequate input validation and output escaping mechanisms within the CMS Made Simple framework. The application accepts user-supplied IP address exclusions without proper sanitization, allowing attackers to inject malicious script code that gets stored in the system configuration. This stored data is subsequently rendered in the web interface without appropriate HTML encoding or context-aware output filtering, enabling the execution of arbitrary JavaScript code in the victim's browser context. The vulnerability is classified as a stored XSS due to the persistence of the malicious payload in the application's database rather than a reflected or DOM-based variant.
The operational impact of this vulnerability is significant as it provides attackers with a persistent foothold within the CMS environment. Once exploited, the malicious script can perform various malicious activities including stealing session cookies, redirecting users to malicious sites, defacing content, or establishing command and control channels. The authenticated nature of the attack means that an attacker only needs valid user credentials to compromise the system, which could be obtained through various social engineering or credential compromise techniques. This vulnerability essentially allows an attacker to execute arbitrary code within the context of the victim's browser, potentially leading to complete account takeover or further escalation within the web application environment.
Organizations affected by this vulnerability should immediately implement mitigations including applying the latest security patches released by CMS Made Simple, implementing proper input validation and output encoding mechanisms, and conducting comprehensive security assessments of their CMS configurations. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws, and can be mapped to ATT&CK technique T1566.001 for initial access through malicious web content. Additionally, implementing web application firewalls and content security policies can provide additional layers of protection against such attacks, while regular security monitoring and user access controls should be enforced to limit potential exploitation opportunities.