CVE-2020-21930 in Eyoucms
Summary
by MITRE • 08/11/2021
A stored cross site scripting (XSS) vulnerability in the web_attr_2 field of Eyoucms v1.4.1 allows authenticated attackers to execute arbitrary web scripts or HTML.
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Analysis
by VulDB Data Team • 08/16/2021
The vulnerability CVE-2020-21930 represents a critical stored cross site scripting flaw within the Eyoucms content management system version 1.4.1. This vulnerability specifically affects the web_attr_2 field, which serves as a parameter for storing web attributes within the system's database. The flaw enables authenticated attackers who have already gained access to the system to inject malicious scripts that persist in the database and execute whenever the affected field is rendered in web pages. The vulnerability stems from insufficient input validation and output sanitization mechanisms that fail to properly escape or filter user-supplied data before it is stored and subsequently displayed to other users.
From a technical perspective, this vulnerability operates as a stored XSS attack where malicious payloads are permanently stored in the application's database rather than being reflected in the HTTP request. The web_attr_2 field becomes a vector for script injection, allowing attackers to embed malicious JavaScript code, HTML tags, or other harmful content that executes in the context of other users' browsers. The authenticated nature of this vulnerability means that attackers must first compromise legitimate credentials, but once inside the system, they can manipulate stored data to compromise other users. This flaw directly maps to CWE-79 which defines cross site scripting as the failure to properly neutralize user input data when it is used in dynamic web content generation.
The operational impact of CVE-2020-21930 extends beyond simple script execution, as it can enable attackers to perform a wide range of malicious activities including session hijacking, credential theft, data exfiltration, and redirection to malicious sites. When exploited, the vulnerability can allow attackers to escalate privileges, modify content, or gain unauthorized access to sensitive information within the CMS. The persistent nature of stored XSS means that the malicious scripts will continue to execute for all users who view the affected content, potentially affecting hundreds or thousands of users depending on the scope of the compromised system. This vulnerability aligns with ATT&CK technique T1566 which covers social engineering tactics through the manipulation of web content to deceive users into executing malicious code.
Organizations affected by this vulnerability should prioritize immediate remediation through the application of security patches released by the Eyoucms developers or by implementing compensating controls such as input validation filters, output encoding, and proper sanitization of user inputs. The implementation of a web application firewall can provide additional protection by detecting and blocking malicious payloads before they reach the application layer. Security monitoring should include detection of unusual data modifications in the web_attr_2 field, and regular security assessments should verify that all user inputs are properly sanitized before database storage. The vulnerability demonstrates the critical importance of proper input validation and output encoding practices in web applications, particularly when dealing with fields that are expected to contain user-generated content. Organizations should also consider implementing principle of least privilege controls to limit the scope of potential damage from authenticated attacks, ensuring that users have only the necessary permissions to perform their required functions within the system.