CVE-2016-4567 in MediaElement.js
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in flash/FlashMediaElement.as in MediaElement.js before 2.21.0, as used in WordPress before 4.5.2, allows remote attackers to inject arbitrary web script or HTML via the query string.
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Analysis
by VulDB Data Team • 10/01/2024
The vulnerability described in CVE-2016-4567 represents a critical cross-site scripting flaw within the MediaElement.js library that was widely deployed in WordPress environments. This issue specifically affects the Flash media player component located in the flash/FlashMediaElement.as file, which serves as a fallback mechanism for multimedia content playback in older browsers that do not support HTML5 media elements. The vulnerability exists in versions prior to 2.21.0 of MediaElement.js and was particularly dangerous because it was integrated into WordPress versions before 4.5.2, exposing millions of websites to potential exploitation. The flaw allows remote attackers to execute malicious scripts by manipulating the query string parameters passed to the media player component, creating a pathway for persistent cross-site scripting attacks that could compromise user sessions and data.
The technical nature of this vulnerability stems from insufficient input validation and output encoding within the Flash media player's parameter handling mechanism. When user-supplied query string parameters are processed by the FlashMediaElement.as component without proper sanitization, the system fails to escape or filter potentially malicious content that could contain script tags or other HTML elements. This weakness directly maps to CWE-79, which defines Cross-Site Scripting vulnerabilities as a result of improper validation or encoding of user-provided data. The attack vector is particularly insidious because it leverages the Flash player's ability to execute code in the browser context, bypassing standard HTML sanitization measures that typically protect against XSS attacks in regular web applications. The vulnerability creates a persistent threat where attackers can embed malicious JavaScript code within the query parameters, which then executes when legitimate users interact with the media player component.
The operational impact of this vulnerability extends far beyond simple script injection, as it provides attackers with a sophisticated means to compromise user sessions and steal sensitive information from WordPress installations. When exploited, the XSS flaw enables attackers to execute malicious code in the context of the victim's browser, potentially allowing them to access cookies, session tokens, and other sensitive data that could be used to impersonate users or gain administrative access to WordPress sites. This vulnerability particularly affects WordPress installations that rely on the MediaElement.js library for audio and video playback functionality, which was common across numerous websites including blogs, news portals, and corporate sites. The attack can be amplified through social engineering techniques where users are directed to malicious URLs containing the exploit, making it a significant threat to both individual users and website administrators who may not immediately recognize the compromised state of their media player components.
The remediation strategy for CVE-2016-4567 requires immediate updates to both the MediaElement.js library and affected WordPress installations to ensure proper input validation and output encoding of query parameters. System administrators must upgrade to MediaElement.js version 2.21.0 or later, which includes proper sanitization measures for user input, and simultaneously update WordPress to version 4.5.2 or higher to address the vulnerability at the application level. Additionally, implementing content security policies and input validation at multiple layers can provide defense-in-depth protection against similar vulnerabilities, aligning with ATT&CK technique T1203 for legitimate credential exposure and T1059 for command and scripting interpreter usage. Organizations should also conduct comprehensive security audits of their media player components and implement regular vulnerability scanning to identify and remediate similar issues before they can be exploited by malicious actors in the wild.