CVE-2015-5622 in WordPress
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in WordPress before 4.2.3 allows remote authenticated users to inject arbitrary web script or HTML by leveraging the Author or Contributor role to place a crafted shortcode inside an HTML element, related to wp-includes/kses.php and wp-includes/shortcodes.php.
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Analysis
by VulDB Data Team • 06/03/2022
The CVE-2015-5622 vulnerability represents a critical cross-site scripting flaw in WordPress versions prior to 4.2.3 that specifically targets users with Author or Contributor roles. This vulnerability operates through a sophisticated exploitation vector that leverages the legitimate shortcode functionality within WordPress to execute malicious code in the context of other users' browsers. The flaw exists in the core WordPress filtering mechanisms located in wp-includes/kses.php and wp-includes/shortcodes.php, which are responsible for sanitizing user input and processing shortcode attributes. The vulnerability's exploitation requires an authenticated user with either Author or Contributor privileges, making it particularly concerning for sites with multiple content creators or contributors who may not fully understand security implications.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within WordPress's shortcode processing pipeline. When an authenticated user with Author or Contributor privileges creates a post or page containing a crafted shortcode within an HTML element, the system fails to properly sanitize the shortcode parameters before rendering them. This creates an opportunity for attackers to inject malicious JavaScript code that executes in the browsers of other users who view the affected content. The vulnerability specifically affects the kses.php file which handles the sanitization of HTML content and the shortcodes.php file which processes shortcode attributes, both of which are fundamental components in WordPress's content rendering pipeline. The flaw essentially allows an attacker to bypass the standard content filtering mechanisms that are supposed to prevent malicious code execution.
The operational impact of CVE-2015-5622 extends beyond simple XSS attacks, as it provides attackers with a persistent foothold within WordPress installations. Once exploited, the vulnerability can be used to steal session cookies, redirect users to malicious websites, inject phishing content, or even escalate privileges within the WordPress environment. The fact that this vulnerability affects users with Author or Contributor roles means that even sites with strict user access controls can be compromised if any of these lower-privilege users account is compromised or if attackers gain access to such accounts through social engineering or other means. This creates a significant risk for organizations that rely on content contributor workflows or have multiple editors working on the same site, as the attack surface expands beyond just administrative users.
Organizations affected by this vulnerability should implement immediate mitigations including upgrading to WordPress version 4.2.3 or later, which contains the necessary patches to address the XSS vulnerability. Additionally, administrators should conduct thorough security audits of their WordPress installations to identify any compromised accounts or malicious content that may have been injected prior to the patch release. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in software applications, and demonstrates the importance of proper input validation and output encoding in web applications. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access through web application exploitation and privilege escalation through content management system vulnerabilities. Security teams should also consider implementing additional monitoring for unusual shortcode usage patterns and content modifications by users with Author or Contributor roles, as these activities may indicate potential exploitation attempts.