CVE-2021-24671 in MX Time Zone Clocks Plugin
Summary
by MITRE • 09/28/2021
The MX Time Zone Clocks WordPress plugin before 3.4.1 does not escape the time_zone attribute of the mxmtzc_time_zone_clocks shortcode, allowing users with a role as low as Contributor to perform Stored Cross-Site Scripting attacks
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Analysis
by VulDB Data Team • 10/03/2021
The vulnerability identified as CVE-2021-24671 affects the MX Time Zone Clocks WordPress plugin version 3.4.0 and earlier, representing a critical security flaw that undermines the integrity of web applications utilizing this plugin. This issue stems from inadequate input sanitization within the plugin's shortcode implementation, specifically concerning the time_zone attribute parameter. The vulnerability permits attackers with minimal privileges to execute stored cross-site scripting attacks, demonstrating a significant weakness in the plugin's security architecture and highlighting the importance of proper data validation and output escaping in web applications.
The technical flaw manifests in the plugin's failure to properly escape the time_zone attribute when processing the mxmtzc_time_zone_clocks shortcode. This oversight creates a persistent XSS vulnerability that allows malicious actors to inject arbitrary JavaScript code into the plugin's output. The vulnerability is particularly concerning because it requires only Contributor-level user roles to exploit, which typically have limited capabilities within WordPress environments. The stored nature of this XSS means that the malicious script persists in the database and executes whenever the affected page is loaded, potentially compromising multiple users who view the compromised content. This vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws and represents a classic case of insufficient output escaping in web applications.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform various malicious activities including session hijacking, data theft, and unauthorized administrative actions. Attackers could potentially escalate privileges by stealing administrator cookies or injecting additional malicious code that could compromise the entire WordPress installation. The stored nature of the vulnerability means that the attack vector remains active until the malicious code is removed from the database, creating a persistent threat that could affect all users who access pages containing the compromised shortcode. This type of vulnerability also aligns with ATT&CK technique T1566 which covers social engineering tactics and can be leveraged to establish initial access or maintain persistence within targeted environments.
The security implications of CVE-2021-24671 underscore the critical importance of proper input validation and output escaping in web application development. The vulnerability demonstrates how seemingly minor oversights in code can create significant security risks, particularly when dealing with user-controllable parameters that are directly embedded into web page output. Organizations using the affected plugin version should immediately implement mitigations including updating to version 3.4.1 or later, which includes proper sanitization of the time_zone attribute. Additionally, administrators should review and audit existing content for potential malicious injections, implement content security policies, and consider restricting contributor-level permissions for shortcode usage where possible. The vulnerability also highlights the necessity of regular security audits and the importance of keeping all plugins and themes updated to address known security issues and maintain a robust defense-in-depth strategy against evolving threats.