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Attack Tree Analysis for adam-p/markdown-here

Objective: Execute Arbitrary JavaScript (XSS) via Markdown Here

Attack Tree Visualization

Goal: Execute Arbitrary JavaScript (XSS) via Markdown Here ├── 1. Bypass Sanitization (Markdown-it Vulnerabilities) [CRITICAL] │ ├── 1.1 Exploit known markdown-it CVEs (if unpatched) [HIGH RISK] │ └── 1.3 Exploit misconfiguration of markdown-it options [HIGH RISK] │ ├── 1.3.1 html: true enabled (allows raw HTML) - Inject <script> tags directly. [CRITICAL] │ └── 1.3.2 linkify: true with insufficient URL validation - Craft malicious URLs (e.g., javascript:alert(1)). [CRITICAL] ├── 2. Exploit Markdown Here Specific Features/Bugs │ ├── 2.2 Code Highlighting (highlight.js) Vulnerabilities │ │ ├── 2.2.1 Exploit known highlight.js CVEs (if unpatched) [HIGH RISK] │ ├── 2.4 Math Rendering (KaTeX/MathJax) Vulnerabilities │ ├── 2.4.1 Exploit known KaTeX/MathJax CVEs [HIGH RISK] └── 3. Exploit Interactions with Other Libraries/Components └── 3.2 If Markdown Here output is directly inserted into a vulnerable DOM context (e.g., without proper escaping), exploit that. [CRITICAL]

Attack Tree Path: 1. Bypass Sanitization (Markdown-it Vulnerabilities) [CRITICAL]

  • Description: This is the foundation of most attacks. Markdown-it is responsible for converting Markdown to HTML and sanitizing it to prevent XSS. If this sanitization can be bypassed, the attacker can inject malicious JavaScript.
  • Why Critical: It's the core component; failure here compromises the entire system.

Attack Tree Path: 1.1 Exploit known markdown-it CVEs (if unpatched) [HIGH RISK]

  • Description: If the application uses an outdated version of markdown-it with known Common Vulnerabilities and Exposures (CVEs), an attacker can craft malicious Markdown input that exploits these vulnerabilities to execute arbitrary JavaScript.
  • Attack Vector:
    • The attacker identifies a known CVE in the specific version of markdown-it used by the application.
    • The attacker crafts a Markdown payload specifically designed to trigger the vulnerability. This payload might involve unusual character sequences, malformed HTML tags (if partially allowed), or other techniques specific to the CVE.
    • The attacker submits this malicious Markdown to the application.
    • If the application is vulnerable, markdown-it fails to properly sanitize the input, and the injected JavaScript executes in the user's browser.
  • Mitigation: Keep markdown-it updated to the latest version. Use dependency management tools and vulnerability scanners.

Attack Tree Path: 1.3 Exploit misconfiguration of markdown-it options [HIGH RISK]

  • Description: markdown-it has several configuration options that, if misused, can create significant security vulnerabilities.
  • Why High Risk: Easy to exploit, high impact.

Attack Tree Path: 1.3.1 html: true enabled (allows raw HTML) - Inject <script> tags directly. [CRITICAL]

  • Description: This is the most dangerous misconfiguration. If html: true is set, markdown-it will not sanitize raw HTML embedded within the Markdown. This allows an attacker to directly inject <script> tags containing arbitrary JavaScript.
  • Attack Vector:
    • Attacker submits Markdown containing: <script>alert('XSS');</script>
    • markdown-it passes the HTML through unchanged.
    • The browser executes the script.
  • Mitigation: Never enable html: true unless absolutely necessary, and if you do, implement a robust, independent HTML sanitization library (like DOMPurify) after markdown-it processing. This is still risky.
  • Why Critical: Direct, trivial XSS.

Attack Tree Path: 1.3.2 linkify: true with insufficient URL validation - Craft malicious URLs (e.g., javascript:alert(1)).[CRITICAL]

  • Description: If linkify: true is enabled, markdown-it automatically converts text that looks like a URL into a clickable link. However, if the URL validation is weak or absent, an attacker can create links using the javascript: protocol, which executes JavaScript when clicked.
  • Attack Vector:
    • Attacker submits Markdown containing: [Click me](javascript:alert('XSS'))
    • markdown-it creates an <a> tag with the malicious href.
    • When a user clicks the link, the JavaScript executes.
  • Mitigation: Use a strong URL allowlist or a robust URL sanitization library to ensure that only safe protocols (like http: and https:) are allowed. Never allow javascript: URLs.
  • Why Critical: Common and easily overlooked vulnerability.

Attack Tree Path: 2. Exploit Markdown Here Specific Features/Bugs

Attack Tree Path: 2.2 Code Highlighting (highlight.js) Vulnerabilities

Attack Tree Path: 2.2.1 Exploit known highlight.js CVEs (if unpatched) [HIGH RISK]

  • Description: Similar to markdown-it, if an unpatched version of highlight.js is used, attackers can craft malicious code blocks to exploit known vulnerabilities.
  • Attack Vector:
    • Attacker identifies a known CVE in the highlight.js version.
    • Attacker crafts a code block designed to trigger the vulnerability.
    • The crafted code block, when processed, leads to JavaScript execution.
  • Mitigation: Keep highlight.js updated.

Attack Tree Path: 2.4 Math Rendering (KaTeX/MathJax) Vulnerabilities

Attack Tree Path: 2.4.1 Exploit known KaTeX/MathJax CVEs [HIGH RISK]

  • Description: Math rendering libraries can also have vulnerabilities. Unpatched versions are susceptible to crafted malicious math expressions.
  • Attack Vector:
    • Attacker identifies a known CVE in the KaTeX/MathJax version.
    • Attacker crafts a malicious math expression to trigger the vulnerability.
    • The expression, when rendered, executes JavaScript.
  • Mitigation: Keep KaTeX/MathJax updated.

Attack Tree Path: 3. Exploit Interactions with Other Libraries/Components

Attack Tree Path: 3.2 If Markdown Here output is directly inserted into a vulnerable DOM context (e.g., without proper escaping), exploit that. [CRITICAL]

  • Description: Even if Markdown Here and its dependencies are perfectly secure and configured correctly, the application itself can still introduce an XSS vulnerability if it doesn't properly handle the output from Markdown Here. This is a general web security issue, but it's crucial in this context.
  • Attack Vector:
    • Markdown Here sanitizes the input and produces safe HTML.
    • The application takes this HTML and inserts it directly into the DOM without proper escaping or encoding. For example, it might use innerHTML directly on an element without first sanitizing the output.
    • If the output contains any characters that have special meaning in HTML (like <, >, &, `