CVE-2021-23327 in apexcharts
Summary
by MITRE • 02/09/2021
The package apexcharts before 3.24.0 are vulnerable to Cross-site Scripting (XSS) via lack of sanitization of graph legend fields.
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Analysis
by VulDB Data Team • 02/25/2021
The vulnerability identified as CVE-2021-23327 affects the apexcharts JavaScript library version 3.24.0 and earlier, representing a critical cross-site scripting weakness that compromises web application security. This issue specifically targets the graph legend fields within the visualization library, where insufficient input sanitization allows malicious actors to inject arbitrary JavaScript code through user-controlled data that gets rendered in chart legends. The vulnerability exists in the library's handling of legend labels and data attributes, creating an attack surface where attackers can manipulate chart elements to execute malicious scripts in the context of the victim's browser.
The technical flaw stems from improper sanitization of user-supplied data within the legend rendering functionality of the apexcharts library. When developers pass user-generated content or untrusted data into chart legend fields, the library fails to adequately escape or filter special characters that could be interpreted as HTML or JavaScript code. This vulnerability falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, which specifically addresses the failure to properly sanitize user input before incorporating it into web content. The flaw manifests when the library processes legend text, data labels, or other dynamic content without implementing proper output encoding mechanisms that would prevent script execution.
The operational impact of this vulnerability extends beyond simple XSS exploitation, as it can enable attackers to perform session hijacking, defacement of web applications, data theft, and redirection to malicious sites. When exploited, the vulnerability allows attackers to inject malicious scripts that can steal cookies, access sensitive data, or redirect users to phishing sites. The attack typically requires a user to view a vulnerable chart containing maliciously crafted legend data, making this a client-side vulnerability that leverages social engineering or pre-existing data manipulation capabilities. This vulnerability particularly affects web applications that rely heavily on data visualization and charting libraries, including dashboards, analytics platforms, and reporting systems where user input is displayed in graphical formats.
Mitigation strategies for CVE-2021-23327 primarily involve upgrading to apexcharts version 3.24.0 or later, which includes proper input sanitization and output encoding for legend fields. Organizations should also implement comprehensive input validation and sanitization practices within their applications, ensuring that all user-supplied data passed to charting libraries undergoes proper escaping before rendering. The remediation process should include thorough code reviews to identify all instances where chart legends or labels might receive untrusted input, and implementing proper content security policies to limit the impact of potential exploitation. Additionally, developers should consider implementing the principle of least privilege when configuring chart properties, avoiding direct injection of user data into critical rendering elements and instead using safe data transformation processes that prevent script injection while maintaining functionality. This vulnerability aligns with ATT&CK technique T1203 - Exploitation for Client Execution, where attackers leverage client-side vulnerabilities to execute malicious code in user browsers, making proper library updates and input validation essential defensive measures.