CVE-2020-4046 in WordPress
Summary
by MITRE
In affected versions of WordPress, users with low privileges (like contributors and authors) can use the embed block in a certain way to inject unfiltered HTML in the block editor. When affected posts are viewed by a higher privileged user, this could lead to script execution in the editor/wp-admin. This has been patched in version 5.4.2, along with all the previously affected versions via a minor release (5.3.4, 5.2.7, 5.1.6, 5.0.10, 4.9.15, 4.8.14, 4.7.18, 4.6.19, 4.5.22, 4.4.23, 4.3.24, 4.2.28, 4.1.31, 4.0.31, 3.9.32, 3.8.34, 3.7.34).
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Analysis
by VulDB Data Team • 10/24/2020
The vulnerability described in CVE-2020-4046 represents a significant security flaw within the WordPress content management system that allows users with minimal privileges to execute potentially dangerous code within the administrative environment. This issue specifically affects WordPress versions prior to 5.4.2 and impacts users with roles such as contributors and authors who typically have limited capabilities within the system. The flaw exists within the embed block functionality of the block editor, which is a core component of WordPress's modern editing interface. The vulnerability is categorized under CWE-79, which represents Cross-Site Scripting (XSS) attacks, specifically in the context of unfiltered HTML injection. The attack vector exploits the trust relationship between lower-privilege users and the WordPress administrative interface, creating a privilege escalation scenario that could have severe implications for system security.
The technical implementation of this vulnerability relies on the improper sanitization of HTML content within the embed block feature. When users with contributor or author roles create posts containing specially crafted embed blocks, they can inject unfiltered HTML code that bypasses the normal security restrictions imposed on their user roles. This code injection occurs during the post creation process within the block editor, where the system fails to properly validate or sanitize the embedded content before it is stored in the database. The vulnerability specifically targets the WordPress block editor's handling of embed content, which is designed to allow users to embed external media and content from various sources. When these posts are later viewed by users with higher privileges such as administrators or editors, the malicious HTML code executes within the context of the privileged user's browser session, effectively creating a sandbox escape scenario.
The operational impact of CVE-2020-4046 extends beyond simple code injection, as it creates a pathway for attackers to escalate privileges and potentially gain full administrative control over WordPress installations. When higher-privileged users access posts containing the maliciously injected HTML, the code executes in the editor context, which provides access to sensitive administrative functions and data. This vulnerability directly aligns with ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation," and T1547, which addresses "Registry Run Keys / Startup Folder' techniques, as the injected code could potentially establish persistence mechanisms. The vulnerability has been classified as a critical threat because it allows attackers with minimal privileges to compromise the security of the entire WordPress installation by leveraging the trust relationship between different user roles.
The remediation for this vulnerability required immediate patching across multiple WordPress versions, with WordPress 5.4.2 serving as the primary fix and multiple minor releases providing backward compatibility patches for older versions. This approach demonstrates the severity of the issue and the need for comprehensive vulnerability management across different WordPress versions. Security professionals should consider this vulnerability when conducting WordPress security assessments and implementing security controls, as it highlights the importance of proper input sanitization and privilege separation within content management systems. The patch implementation addresses the core issue by enforcing stricter HTML sanitization rules within the embed block functionality and ensuring that all content generated by lower-privilege users is properly validated before being stored or rendered in contexts accessible to higher-privilege users. Organizations should prioritize updating their WordPress installations to the patched versions and implement additional security monitoring to detect potential exploitation attempts.