CVE-2016-5834 in WordPress
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the wp_get_attachment_link function in wp-includes/post-template.php in WordPress before 4.5.3 allows remote attackers to inject arbitrary web script or HTML via a crafted attachment name, a different vulnerability than CVE-2016-5833.
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Analysis
by VulDB Data Team • 08/24/2022
The cross-site scripting vulnerability identified as CVE-2016-5834 affects WordPress versions prior to 4.5.3 and resides within the wp_get_attachment_link function located in wp-includes/post-template.php. This flaw represents a classic server-side XSS vulnerability that enables remote attackers to inject malicious scripts into web pages viewed by other users. The vulnerability specifically manifests when WordPress processes attachment names that contain crafted malicious content, allowing attackers to bypass normal input sanitization mechanisms that should protect against such attacks.
The technical implementation of this vulnerability stems from insufficient output escaping of attachment names within the wp_get_attachment_link function. When WordPress generates links for media attachments, it fails to properly sanitize or escape special characters in attachment filenames before incorporating them into HTML output. This oversight creates an opening for attackers to embed malicious JavaScript code, HTML tags, or other harmful content within attachment names that get rendered directly into web pages without proper context-aware escaping. The vulnerability operates at the presentation layer where user-provided data transitions from input to output rendering, making it particularly dangerous for content management systems that handle diverse user-generated content.
The operational impact of CVE-2016-5834 extends beyond simple script injection, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, redirection to malicious sites, and data exfiltration. When victims view pages containing compromised attachment links, their browsers execute the injected scripts in the context of the vulnerable WordPress site, potentially allowing attackers to steal cookies, modify page content, or redirect users to phishing sites. The vulnerability is particularly concerning for WordPress installations that allow user uploads, as attackers can upload files with malicious names and then wait for users to view these attachments, creating a persistent attack vector that can affect multiple visitors over time.
This vulnerability aligns with CWE-79 which specifically addresses Cross-Site Scripting flaws in software applications, and maps to ATT&CK technique T1566.001 for "Phishing: Spearphishing Attachment" where attackers leverage XSS vulnerabilities to deliver malicious payloads through seemingly legitimate file attachments. The flaw demonstrates poor input validation and output escaping practices that are commonly exploited in web application security breaches. Organizations using vulnerable WordPress installations face significant risk of user compromise and potential unauthorized access to sensitive information, particularly in environments where users may encounter untrusted file attachments from various sources.
The recommended mitigation strategy involves upgrading to WordPress version 4.5.3 or later, which includes proper output escaping mechanisms for attachment names. Additionally, administrators should implement proper input validation for file uploads, employ Content Security Policy headers to limit script execution, and conduct regular security audits of user-uploaded content. Organizations should also consider implementing web application firewalls and monitoring for suspicious attachment names that may contain common XSS payload patterns. Regular security patching and vulnerability assessment procedures become critical in maintaining protection against similar flaws that may exist in other WordPress components or third-party plugins that could present analogous XSS attack surfaces.