CVE-2020-4049 in WordPress
Summary
by MITRE
In affected versions of WordPress, when uploading themes, the name of the theme folder can be crafted in a way that could lead to JavaScript execution in /wp-admin on the themes page. This does require an admin to upload the theme, and is low severity self-XSS. 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
This vulnerability exists within the WordPress content management system where improper input validation during theme uploads creates a path for maliciously crafted theme folder names to execute JavaScript code within the administrative interface. The flaw specifically affects the wp-admin themes page where administrators can upload and manage themes, making it a self-XSS vector that requires administrative privileges to exploit. The vulnerability stems from insufficient sanitization of theme directory names during the upload process, allowing attackers to inject malicious JavaScript payloads that execute in the context of the admin user's browser session.
The technical implementation of this vulnerability involves the manipulation of theme folder naming conventions during the upload process. When WordPress processes theme uploads, it fails to adequately validate or sanitize the directory names provided by users, particularly when these names contain special characters or sequences that could be interpreted as HTML or JavaScript code. This creates an environment where a crafted theme folder name can contain embedded script tags or other malicious code that executes when the admin user navigates to the themes page. The vulnerability is classified as low severity self-XSS according to CWE-79, which specifically addresses cross-site scripting flaws in web applications where the attacker's input is reflected back to the user's browser without proper sanitization.
The operational impact of this vulnerability is significant for WordPress administrators who may be tricked into uploading malicious themes or who have their accounts compromised through social engineering attacks. The attack requires an administrative account to successfully execute, making it less likely to be exploited at scale but still dangerous in targeted scenarios. The vulnerability affects multiple WordPress versions from 3.8 through 5.4, with patches released in both the current version and several previously affected minor releases, demonstrating the importance of maintaining updated WordPress installations. Attackers could potentially use this vector to steal admin session cookies, modify site content, or perform other malicious activities within the WordPress admin interface.
Mitigation strategies for this vulnerability include immediate patching of all affected WordPress versions to the latest releases, implementing strict access controls for theme uploads, and conducting regular security audits of uploaded themes. Organizations should also consider implementing additional security measures such as web application firewalls that can detect and block malicious theme uploads, along with user education to prevent administrators from uploading untrusted themes. The patch addresses the issue by implementing proper input sanitization and validation of theme directory names during the upload process, ensuring that any potentially malicious code sequences are properly escaped or removed before the theme is processed. This fix aligns with ATT&CK technique T1059.007 for command and scripting interpreter, specifically targeting the execution of malicious code through web-based interfaces and user interaction requirements that are common in self-XSS attacks.