CVE-2017-17092 in WordPress
Summary
by MITRE
wp-includes/functions.php in WordPress before 4.9.1 does not require the unfiltered_html capability for upload of .js files, which might allow remote attackers to conduct XSS attacks via a crafted file.
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Analysis
by VulDB Data Team • 01/16/2023
The vulnerability identified as CVE-2017-17092 resides within the WordPress content management system and specifically affects versions prior to 4.9.1. This flaw is particularly concerning because it undermines the security controls designed to prevent cross-site scripting attacks through improper file upload validation. The vulnerability is located in the wp-includes/functions.php file which serves as a core component responsible for handling various administrative functions including file management operations. The issue stems from the insufficient capability checks that govern file uploads, creating a pathway for malicious actors to bypass intended security restrictions.
The technical implementation flaw involves the WordPress system's failure to properly validate user capabilities when processing javascript file uploads. Specifically, the system does not require the unfiltered_html capability for uploading .js files, which represents a significant deviation from expected security practices. This omission allows users with lower privileges to upload javascript files that could contain malicious payloads. The vulnerability operates under the principle that certain file types should be restricted based on user permissions, particularly when those files could be executed within the browser context of a website. When an attacker uploads a crafted javascript file, the system's inadequate validation allows the file to be processed and potentially executed, creating an environment conducive to cross-site scripting attacks.
The operational impact of this vulnerability extends beyond simple file upload manipulation and represents a serious threat to website security and user data integrity. Attackers can leverage this weakness to inject malicious javascript code that can perform actions such as stealing cookies, session tokens, or other sensitive information from authenticated users. The vulnerability particularly affects sites where users have the ability to upload files, which in many cases includes contributors or authors who may not have full administrative privileges. This creates a scenario where less privileged users can potentially compromise the entire website through the execution of malicious scripts. The implications are significant as these attacks can persist across user sessions and can be used to maintain persistent access to compromised systems.
The vulnerability aligns with several cybersecurity frameworks and threat models including CWE-22, which addresses improper limitation of a pathname to a restricted directory, and CWE-79, which covers cross-site scripting vulnerabilities. From an ATT&CK perspective, this weakness maps to T1059.007 for scripting languages and T1566 for social engineering techniques that could be employed to deliver the malicious javascript payloads. The attack surface is particularly broad as it affects WordPress installations across various configurations and user roles, making it a prime target for automated exploitation tools. Organizations using affected versions of WordPress should immediately implement mitigations including updating to version 4.9.1 or later, implementing additional file validation controls, and monitoring for suspicious file upload activities. The vulnerability demonstrates the critical importance of proper capability checks and access controls in web application security, particularly when dealing with executable file types that can be directly interpreted by web browsers.