CVE-2023-0873 in Kanban Boards Plugin
Summary
by MITRE • 06/27/2023
The Kanban Boards for WordPress plugin before 2.5.21 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 • 07/20/2023
The vulnerability identified as CVE-2023-0873 affects the Kanban Boards for WordPress plugin version 2.5.20 and earlier, representing a critical security flaw that enables stored cross-site scripting attacks through improper input sanitization. This vulnerability specifically targets high-privilege users such as administrators who possess the capability to modify plugin settings, creating a significant risk in multi-site WordPress environments where the unfiltered_html capability is typically restricted to prevent malicious script injection. The flaw exists in the plugin's handling of user-provided data within its configuration settings, where insufficient sanitization and escaping mechanisms fail to properly validate or encode potentially malicious input before storing it in the database.
The technical implementation of this vulnerability stems from the plugin's failure to apply proper output escaping and input sanitization routines to its settings parameters. When administrators configure the kanban board plugin, they can input various data elements including board names, task descriptions, and other customizable fields that are subsequently stored in the WordPress database. Without adequate sanitization, malicious scripts entered by an attacker with admin privileges can be persisted in the database and executed whenever the affected plugin renders these stored values in the user interface. This stored XSS vulnerability operates through the standard mechanism where user-supplied content is reflected back to other users without proper HTML entity encoding, allowing attackers to inject malicious JavaScript code that executes in the context of other users' browsers.
The operational impact of CVE-2023-0873 extends beyond simple script execution as it provides attackers with elevated privileges within the WordPress environment. In multi-site setups where the unfiltered_html capability is disabled, attackers can leverage this vulnerability to bypass security restrictions that normally protect against direct HTML injection. This creates a persistent threat vector where malicious code can be executed in the context of administrator sessions, potentially allowing for complete compromise of the WordPress installation. The vulnerability is particularly concerning in enterprise environments where WordPress is used for business-critical applications, as it enables attackers to establish persistent backdoors, steal session cookies, or perform further attacks against the underlying infrastructure. The stored nature of the vulnerability means that the malicious scripts remain active even after the initial injection, creating a long-term threat that can persist across multiple user sessions and system restarts.
The vulnerability aligns with CWE-79 which defines Cross-Site Scripting as a weakness where untrusted data is incorporated into web page content without proper validation or encoding. This weakness specifically manifests as a stored XSS attack pattern where malicious input is stored on the server and then served to other users without proper sanitization. From an ATT&CK framework perspective, this vulnerability maps to T1566.001 - Phishing via Service and T1059.001 - Command and Scripting Interpreter, as attackers can use the stored XSS to deliver malicious payloads and establish command execution capabilities. The vulnerability also intersects with T1190 - Exploit Public-Facing Application, as it represents an exploitable weakness in a widely used WordPress plugin that exposes administrative interfaces to attack. Organizations should prioritize immediate patching to version 2.5.21 or later, implement proper input validation measures, and conduct security audits of other plugins to identify similar sanitization issues that could present comparable risks to their WordPress installations.
The remediation approach for CVE-2023-0873 requires immediate deployment of the patched plugin version 2.5.21 which implements proper sanitization and escaping routines for all user-provided settings. Security administrators should also consider implementing additional protective measures such as content security policy headers, regular security scanning of plugin installations, and monitoring for unauthorized changes to plugin configurations. Organizations should conduct comprehensive vulnerability assessments to identify other plugins that may suffer from similar sanitization flaws, as the vulnerability pattern suggests that similar issues could exist in other WordPress plugins that handle user input through administrative interfaces. The incident highlights the critical importance of proper input validation and output escaping in web applications, particularly in environments where privileged users have the ability to modify application behavior through configuration parameters.