CVE-2017-6589 in EpicEditor
Summary
by MITRE
EpicEditor through 0.2.3 has Cross-Site Scripting because of an insecure default marked.js configuration. An example attack vector is a crafted IMG element in an HTML document.
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Analysis
by VulDB Data Team • 09/05/2020
CVE-2017-6589 represents a cross-site scripting vulnerability in EpicEditor version 0.2.3 and earlier, stemming from an insecure default configuration within the marked.js library. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which occurs when an application incorporates untrusted data into web pages without proper validation or sanitization. The flaw specifically resides in how EpicEditor handles HTML content processing through marked.js, a popular markdown parser that converts markdown text into HTML. When users input markdown content containing malicious HTML elements, particularly crafted img tags, the insecure default configuration fails to properly sanitize the output, allowing attackers to inject malicious scripts that execute in the context of other users' browsers.
The technical implementation of this vulnerability exploits the default behavior of marked.js, which by default does not sanitize HTML output from markdown parsing. When EpicEditor processes user input containing malicious HTML elements such as img tags with javascript: protocols or data URLs, the marked.js library renders these elements without adequate filtering. This creates an environment where attackers can craft malicious markdown content that, when processed by the editor, results in script execution within the victim's browser context. The vulnerability is particularly concerning because it affects the core functionality of the editor where users expect to be able to input HTML content safely.
The operational impact of CVE-2017-6589 extends beyond simple script injection, as it enables attackers to perform session hijacking, data theft, and other malicious activities. When exploited, this vulnerability allows attackers to execute arbitrary JavaScript code in the victim's browser, potentially leading to complete compromise of user sessions and access to sensitive information. The attack vector specifically targets the processing of HTML elements within markdown content, making it particularly dangerous in collaborative environments where multiple users contribute to the same documents. This vulnerability aligns with ATT&CK technique T1213.002 for Data from Information Repositories, as it allows attackers to access and manipulate content within document editing systems.
Mitigation strategies for CVE-2017-6589 require immediate attention through software updates and configuration changes. The primary remediation involves upgrading to a newer version of EpicEditor that properly handles HTML sanitization or implementing custom marked.js configurations with proper sanitization. Organizations should enforce strict input validation and implement Content Security Policy headers to limit the execution of inline scripts. Additionally, developers should consider using dedicated HTML sanitization libraries such as DOMPurify or implementing custom sanitization functions that strip dangerous attributes and elements from HTML output. The vulnerability demonstrates the critical importance of secure default configurations in web applications and highlights the necessity of following security best practices in library integration and HTML processing.