CVE-2021-24633 in Countdown Block Plugin
Summary
by MITRE • 09/28/2021
The Countdown Block WordPress plugin before 1.1.2 does not have authorisation in the eb_write_block_css AJAX action, which allows any authenticated user, such as Subscriber, to modify post contents displayed to users.
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Analysis
by VulDB Data Team • 10/02/2021
The vulnerability identified as CVE-2021-24633 affects the Countdown Block WordPress plugin version 1.1.1 and earlier, representing a critical authorization flaw that undermines the security model of WordPress sites utilizing this plugin. This issue stems from the absence of proper access control mechanisms within the eb_write_block_css AJAX action, creating a pathway for unauthorized modifications to content that is ultimately displayed to end users. The vulnerability specifically targets authenticated users, including those with the lowest privilege level of Subscriber, demonstrating how even minimal user permissions can be exploited to cause significant damage to website content integrity.
The technical implementation of this flaw resides in the plugin's AJAX handling mechanism where the eb_write_block_css action lacks adequate authorization checks. This omission allows any authenticated user to submit malicious requests that modify CSS content associated with the countdown block functionality. The vulnerability operates at the application layer and can be exploited through the WordPress AJAX interface, which is commonly used for dynamic content updates without full page reloads. From a cybersecurity perspective, this represents a classic case of insufficient authorization controls that violates fundamental security principles and can be categorized under CWE-863, which addresses improper authorization in software components. The flaw essentially allows privilege escalation within the context of the plugin's functionality, enabling users with minimal privileges to manipulate content that should be restricted to administrators or editors.
The operational impact of this vulnerability extends beyond simple content modification, as it can be leveraged to inject malicious code or alter the presentation of critical website elements in ways that may affect user experience or even compromise security. An attacker with Subscriber-level access could potentially manipulate countdown timers, change visual styling, or insert misleading information that appears legitimate to end users. This capability significantly undermines the trust model of WordPress sites and can lead to reputational damage, user confusion, or even phishing attempts if the malicious content is crafted appropriately. The vulnerability also aligns with ATT&CK technique T1078.004, which covers legitimate credentials and valid accounts, as it exploits the existing authentication system to perform unauthorized actions within the plugin's scope. The impact is particularly concerning because it does not require elevated privileges or specialized attack vectors, making it accessible to any user who can authenticate to the WordPress site.
Mitigation strategies for CVE-2021-24633 should prioritize immediate plugin updates to version 1.1.2 or later, which contains the necessary authorization fixes. Administrators should also implement comprehensive monitoring of AJAX requests and unusual content modifications within the affected plugin's functionality. Additional defensive measures include restricting access to the WordPress admin interface for non-essential users, implementing role-based access controls that limit the capabilities of low-privilege accounts, and conducting regular security audits of installed plugins. Network-level protections such as web application firewalls can help detect and block malicious AJAX requests targeting the vulnerable endpoint. Organizations should also consider implementing the principle of least privilege, ensuring that users only have the minimum permissions necessary for their roles, and regularly review user accounts and their associated capabilities to prevent unauthorized access to sensitive functions. The vulnerability serves as a reminder of the importance of proper authorization checks in all application components and highlights the critical need for regular security assessments of third-party plugins that integrate with core WordPress functionality.