CVE-2021-24660 in Gutenberg Blocks for Post Grid Plugin
Summary
by MITRE • 09/28/2021
The PostX – Gutenberg Blocks for Post Grid WordPress plugin before 2.4.10, with Saved Templates Addon enabled, allows users with a role as low as Contributor to perform Stored Cross-Site Scripting attacks via the plugin's shortcode.
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Analysis
by VulDB Data Team • 10/03/2021
The vulnerability identified as CVE-2021-24660 affects the PostX Gutenberg Blocks for Post Grid WordPress plugin, specifically when the Saved Templates Addon is enabled. This security flaw represents a critical stored cross-site scripting vulnerability that significantly undermines the plugin's security posture and potentially compromises the entire WordPress installation. The vulnerability exists in versions prior to 2.4.10, making it a widespread concern for WordPress users who have not yet updated their installations.
The technical flaw stems from insufficient input validation and output escaping within the plugin's shortcode handling mechanism. When users with contributor-level permissions create or modify content using the plugin's shortcode functionality, malicious scripts can be injected and stored within the WordPress database. These stored scripts execute whenever the affected shortcode is rendered on the website, creating a persistent XSS vector that can be exploited by attackers who have gained contributor access or higher privileges. The vulnerability specifically impacts the Saved Templates Addon functionality, which allows users to save and reuse content templates, thereby amplifying the attack surface.
The operational impact of this vulnerability is substantial as it enables attackers to execute arbitrary JavaScript code in the context of any user who views pages containing the malicious shortcode. This can lead to session hijacking, credential theft, defacement of content, redirection to malicious sites, and potential privilege escalation within the WordPress environment. The fact that even contributor-level users can exploit this vulnerability means that attackers can leverage compromised accounts with relatively low privileges to cause significant damage. The stored nature of the XSS attack ensures that the malicious code persists until manually removed from the database, making it particularly dangerous for long-term exploitation.
Organizations should immediately update to PostX plugin version 2.4.10 or later to remediate this vulnerability. Additionally, administrators should conduct thorough security audits of their WordPress installations to identify any instances where the Saved Templates Addon is enabled and ensure proper user access controls are in place. Implementing content security policies and regular security monitoring can help detect and prevent exploitation attempts. This vulnerability aligns with CWE-79 (Cross-site Scripting) and maps to ATT&CK technique T1059.007 (Command and Scripting Interpreter: JavaScript) in the context of exploitation. The remediation process should include not only updating the plugin but also reviewing all user roles and permissions to ensure that only trusted administrators have access to template creation and modification features.