CVE-2023-2709 in AN_GradeBook Plugin
Summary
by MITRE • 07/10/2023
The AN_GradeBook WordPress plugin through 5.0.1 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
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Analysis
by VulDB Data Team • 07/16/2023
The CVE-2023-2709 vulnerability resides within the AN_GradeBook WordPress plugin version 5.0.1 and earlier, representing a critical stored cross-site scripting flaw that undermines web application security. This vulnerability specifically targets the plugin's handling of user input within its administrative settings, where insufficient sanitization and escaping mechanisms leave the system exposed to malicious code injection. The flaw is particularly concerning because it affects high-privilege users including administrators who typically possess elevated permissions within WordPress environments. Even when the unfiltered_html capability is restricted - a common security practice in multisite configurations where such capabilities are disabled to prevent arbitrary HTML injection - the vulnerability persists, demonstrating the plugin's inadequate input validation measures.
The technical implementation of this vulnerability stems from the plugin's failure to properly sanitize user-supplied data before storing it in the WordPress database and subsequently rendering it within administrative interfaces. When administrators configure plugin settings, the input values are not adequately escaped or filtered to prevent the execution of malicious JavaScript code. This creates a persistent XSS vector where malicious scripts can be stored in the database and executed whenever the affected administrative pages are accessed. The vulnerability operates under CWE-79 which classifies the issue as a failure to sanitize output, making it a direct descendant of the well-known cross-site scripting weakness that has plagued web applications for decades. The flaw is particularly dangerous in WordPress multisite environments where administrators may assume that restricted capabilities provide sufficient protection against such attacks.
The operational impact of CVE-2023-2709 extends beyond simple script execution, as it enables attackers with administrative privileges to potentially escalate their access and compromise entire WordPress installations. Once a malicious script is stored in the plugin settings, it can execute in the context of any administrator's browser session, potentially allowing attackers to steal authentication tokens, modify user permissions, or even exfiltrate sensitive data. The vulnerability's persistence in multisite environments makes it particularly attractive to attackers targeting large WordPress deployments where administrators may have varying levels of access control. This aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, as the stored payload can execute JavaScript code within the browser context of authenticated users. The attack surface is further expanded because the vulnerability can be leveraged even when standard security measures like unfiltered_html restrictions are in place, rendering typical defense-in-depth strategies ineffective.
Mitigation strategies for CVE-2023-2709 require immediate action from WordPress administrators, beginning with the immediate upgrade to a patched version of the AN_GradeBook plugin if one is available. System administrators should also implement additional defensive measures such as restricting administrative access to only essential personnel, implementing strict input validation at multiple layers, and conducting regular security audits of installed plugins. The vulnerability highlights the importance of proper output escaping and input sanitization practices, particularly when dealing with user-controllable data in administrative interfaces. Organizations should also consider implementing web application firewalls to detect and block suspicious input patterns, and establish monitoring procedures to identify unauthorized changes to plugin configurations. Regular security training for administrators on identifying and responding to such vulnerabilities is essential, as the exploitation of stored XSS vulnerabilities often relies on social engineering or privilege escalation techniques that can be mitigated through proper security awareness practices. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date plugins and the potential consequences of failing to address known security flaws in content management systems.