CVE-2020-35310 in Composr
Summary
by MITRE • 01/26/2021
Composr CMS 10.0.34 is affected by cross-site scripting (XSS) which allows remote attackers to inject an arbitrary web script or HTML via Add Banners in the Description field.
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Analysis
by VulDB Data Team • 05/22/2026
Composr CMS version 10.0.34 contains a cross-site scripting vulnerability that represents a critical security weakness in the content management system's input validation mechanisms. This vulnerability specifically affects the banner management functionality where users can add descriptions through the administrative interface. The flaw exists in the sanitization of user input fields, particularly when processing text content that is later rendered to end users. The vulnerability enables remote attackers to inject malicious scripts or HTML code into the Description field of banner entries, creating a persistent threat vector that can affect all users who view the compromised content.
The technical implementation of this vulnerability stems from inadequate output encoding and input validation within the CMS's banner creation module. When administrators or authorized users enter descriptive text into the banner description field, the system fails to properly sanitize or escape special characters that could be interpreted as executable code by web browsers. This allows attackers to embed malicious javascript payloads, html tags, or other harmful content that executes in the context of other users' browsers when they view the affected banner. The vulnerability operates at the application layer and leverages the trust relationship between the CMS and its end users, making it particularly dangerous as it can be exploited without requiring authentication to the CMS itself.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform a range of malicious activities including session hijacking, credential theft, defacement of website content, and redirection to phishing sites. An attacker who successfully exploits this vulnerability could gain access to administrative sessions if users with elevated privileges view the compromised banner content, potentially leading to complete system compromise. The persistent nature of the vulnerability means that once injected, malicious content remains active until manually removed by administrators, creating a long-term threat vector. This type of vulnerability falls under CWE-79 which specifically addresses cross-site scripting flaws in web applications and aligns with attack patterns described in the MITRE ATT&CK framework under the technique of Web Application Attack.
Mitigation strategies for this vulnerability should include immediate implementation of proper input validation and output encoding mechanisms throughout the CMS. The system should employ comprehensive sanitization of all user-entered content before storage and rendering, using established libraries and frameworks designed to prevent XSS attacks. Administrators should implement content security policies and regularly audit user-generated content for malicious payloads. Additionally, the CMS should be updated to a patched version that addresses this specific vulnerability, as vendors typically release security patches for such flaws. Regular security monitoring and intrusion detection systems should be deployed to identify potential exploitation attempts, while user access controls should be enforced to limit who can add or modify banner content. Organizations should also consider implementing web application firewalls and regular security assessments to prevent similar vulnerabilities from being introduced in future versions or custom implementations.