CVE-2019-19708 in VisualEditor Extension
Summary
by MITRE
The VisualEditor extension through 1.34 for MediaWiki allows XSS via pasted content containing an element with a data-ve-clipboard-key attribute.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 03/10/2024
The vulnerability CVE-2019-19708 represents a cross-site scripting vulnerability within the VisualEditor extension for MediaWiki versions up to 1.34. This flaw specifically arises from insufficient input validation and sanitization when processing content pasted into the editor interface. The vulnerability is particularly concerning because it leverages the data-ve-clipboard-key attribute which is part of MediaWiki's internal clipboard handling mechanism within the VisualEditor. When malicious content containing this attribute is pasted into the editor, it can trigger unintended JavaScript execution in the context of the victim's browser session.
The technical implementation of this vulnerability stems from the way the VisualEditor extension processes clipboard data during paste operations. The extension relies on data-ve-clipboard-key attributes to maintain state information about clipboard contents during editing sessions. However, the extension fails to properly sanitize or escape these attributes when they are rendered back to the user interface. This oversight creates a classic XSS vector where attacker-controlled data can be injected into the page through the editor's rendering process. The vulnerability is classified as CWE-79 - Improper Neutralization of Input During Web Page Generation, which specifically addresses the failure to properly escape or validate user-supplied data before incorporating it into web page content.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to perform a wide range of malicious activities within the context of authenticated users. An attacker could potentially steal session cookies, modify content, redirect users to malicious sites, or even escalate privileges if the target user has administrative capabilities. The vulnerability is particularly dangerous in environments where multiple users interact with MediaWiki, as a single compromised paste operation could affect all users viewing the affected pages. This represents a significant risk to content integrity and user security, especially in collaborative environments where users frequently paste content from external sources.
Mitigation strategies for CVE-2019-19708 should focus on immediate patching of the VisualEditor extension to version 1.35 or later where the vulnerability has been addressed. Organizations should implement strict input validation policies for all clipboard operations and consider disabling the VisualEditor extension temporarily if immediate patching is not feasible. Network-level protections such as content security policies can provide additional defense in depth, though they are not a complete solution. The remediation process should also include user education about the risks of pasting untrusted content into the editor and implementing proper access controls to limit the potential impact of successful exploitation. This vulnerability aligns with ATT&CK technique T1211 - Exploitation for Defense Evasion, as it can be used to establish persistent access through session hijacking or privilege escalation. Organizations should also consider implementing web application firewalls to detect and block malicious clipboard content patterns, though the most effective defense remains the application-level patching and proper input sanitization as defined in CWE-79 guidelines for secure web application development practices.