CVE-2021-24760 in Gutenberg PDF Viewer Block Plugin
Summary
by MITRE • 10/18/2021
The Gutenberg PDF Viewer Block WordPress plugin before 1.0.1 does not sanitise and escape its block, which could allow users with a role as low as Contributor to perform Cross-Site Scripting attacks.
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Analysis
by VulDB Data Team • 10/22/2021
The vulnerability identified as CVE-2021-24760 affects the Gutenberg PDF Viewer Block WordPress plugin version 1.0.0 and earlier, representing a critical cross-site scripting weakness that undermines the security posture of WordPress installations. This issue stems from insufficient sanitization and escaping mechanisms within the plugin's block implementation, creating an attack vector that can be exploited by users possessing minimal privileges. The vulnerability specifically targets the plugin's handling of user-provided input within the Gutenberg editor environment, where the PDF viewer block is rendered.
The technical flaw manifests in the plugin's failure to properly sanitize user input before it is processed and displayed within the block interface. When contributors or users with similar low-privilege roles attempt to insert malicious JavaScript code through the PDF viewer block parameters, the plugin fails to neutralize this content adequately. This lack of input validation creates a persistent cross-site scripting vulnerability that allows attackers to inject malicious scripts into the plugin's output, potentially executing arbitrary code within the context of other users' browsers. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and demonstrates the critical importance of proper input sanitization in web security.
The operational impact of this vulnerability extends beyond simple script execution, as it enables attackers to perform a range of malicious activities including session hijacking, data exfiltration, and privilege escalation within the WordPress environment. Contributors who can create and modify posts are able to inject malicious payloads that persist in the plugin's block rendering, affecting all users who view content containing the vulnerable block. This creates a persistent threat vector that can compromise user sessions and potentially lead to full administrative control of the WordPress installation. The vulnerability's exploitation requires minimal privileges, making it particularly dangerous as it can be leveraged by users who should normally have limited capabilities within the system.
Security mitigations for this vulnerability include immediate upgrading to version 1.0.1 or later of the Gutenberg PDF Viewer Block plugin, which implements proper input sanitization and escaping mechanisms. Administrators should also implement additional security measures such as restricting contributor privileges to prevent unauthorized block modifications, implementing content security policies to limit script execution, and monitoring plugin usage for suspicious activities. The vulnerability demonstrates the importance of adhering to security best practices outlined in the OWASP Top Ten and aligns with ATT&CK technique T1548.001 for privilege escalation through web application vulnerabilities. Regular security audits of WordPress plugins and maintaining updated security configurations are essential defensive measures that help prevent exploitation of similar vulnerabilities in the broader WordPress ecosystem.