CVE-2017-6814 in WordPress
Summary
by MITRE
In WordPress before 4.7.3, there is authenticated Cross-Site Scripting (XSS) via Media File Metadata. This is demonstrated by both (1) mishandling of the playlist shortcode in the wp_playlist_shortcode function in wp-includes/media.php and (2) mishandling of meta information in the renderTracks function in wp-includes/js/mediaelement/wp-playlist.js.
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Analysis
by VulDB Data Team • 12/25/2024
The vulnerability identified as CVE-2017-6814 represents a critical authenticated cross-site scripting flaw in WordPress versions prior to 4.7.3, specifically targeting the media handling functionality within the platform. This vulnerability resides in the playlist shortcode processing mechanism and metadata handling within the media player components, creating a potential attack vector that could be exploited by authenticated users with sufficient privileges to upload media files or modify content. The flaw manifests in two distinct code paths within the WordPress core system, making it particularly concerning as it affects multiple layers of media processing and rendering.
The technical implementation of this vulnerability occurs through the improper sanitization and handling of user-supplied metadata within media files, particularly when processing playlist shortcodes. In wp-includes/media.php, the wp_playlist_shortcode function fails to adequately sanitize input parameters that are passed through the playlist shortcode, while in wp-includes/js/mediaelement/wp-playlist.js, the renderTracks function does not properly escape or validate metadata fields before rendering them in the browser. This dual failure creates a scenario where maliciously crafted media files containing specially formatted metadata can inject arbitrary javascript code that executes in the context of other users' browsers. The vulnerability is classified under CWE-79 as a failure to sanitize user input, specifically in the context of HTML and javascript output.
The operational impact of CVE-2017-6814 extends beyond simple XSS exploitation as it can be leveraged for more sophisticated attacks within a compromised WordPress environment. An authenticated attacker with contributor or higher privileges can upload malicious media files that contain crafted metadata, which then gets processed through the vulnerable functions when other users view the media content or playlist. This creates a persistent threat vector where the malicious code can execute in the browser context of any user who encounters the affected media elements, potentially leading to session hijacking, data exfiltration, or further privilege escalation within the WordPress installation. The attack requires minimal user interaction beyond viewing the affected content, making it particularly dangerous in collaborative environments where multiple users access shared media libraries.
Mitigation strategies for this vulnerability center on immediate patching of WordPress installations to version 4.7.3 or later, which contains the necessary sanitization fixes for both the media.php and wp-playlist.js components. Organizations should also implement additional defensive measures including strict media file upload policies, content validation for metadata fields, and regular security auditing of uploaded media assets. Network-based defenses such as web application firewalls can provide additional protection layers, though the most effective approach remains maintaining up-to-date software versions and implementing proper input validation controls. This vulnerability aligns with ATT&CK technique T1059.007 for command and control through javascript and T1566 for credential access through malicious content, making it a significant concern for organizations that rely on WordPress for content management and user collaboration.