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Threat Model Analysis for github/markup

Threat: Unsanitized HTML Output (XSS)

Description: An attacker injects malicious HTML code within markup input. github/markup or the underlying markup engine fails to sanitize this HTML, rendering it directly in the application's output. The attacker can then execute arbitrary JavaScript in the user's browser.

Impact: User session hijacking, cookie theft, website defacement, redirection to malicious sites, data theft, and other client-side attacks.

Affected Markup Component: Markup Rendering Engine (e.g., Redcarpet, RDiscount, etc.), Output Handling within github/markup.

Risk Severity: High

Mitigation Strategies:

  • Implement a strong Content Security Policy (CSP).
  • Regularly update github/markup and its dependencies.
  • Sanitize the HTML output of github/markup using a dedicated HTML sanitization library before displaying it to users.
  • Employ context-aware output encoding based on where the output is used (e.g., HTML escaping for HTML context).

Threat: Bypassing Sanitization Filters (XSS)

Description: An attacker crafts specific markup input designed to circumvent the sanitization filters implemented by github/markup or the underlying markup engine. This allows malicious HTML to pass through and be rendered.

Impact: Similar to unsanitized HTML output, leading to XSS vulnerabilities and client-side attacks.

Affected Markup Component: Sanitization Logic within github/markup or the Markup Rendering Engine.

Risk Severity: High

Mitigation Strategies:

  • Stay updated on security advisories for github/markup and its dependencies.
  • Conduct regular security testing, including fuzzing and penetration testing, specifically targeting sanitization bypasses.
  • Employ multiple layers of sanitization, potentially using different sanitization libraries or techniques.
  • Favor allow-listing over deny-listing for allowed HTML tags and attributes in sanitization rules.

Threat: Vulnerabilities in Markup Engines (XSS)

Description: The underlying markup engines used by github/markup (e.g., Redcarpet, Kramdown) contain inherent vulnerabilities in their parsing or rendering logic. Attackers can exploit these vulnerabilities by crafting specific markup input that triggers the flaw, leading to malicious HTML injection.

Impact: XSS vulnerabilities originating from flaws in external libraries, resulting in client-side attacks.

Affected Markup Component: External Markup Rendering Engines (Dependencies of github/markup).

Risk Severity: High

Mitigation Strategies:

  • Keep github/markup and all its dependencies, especially markup engines, updated to the latest versions.
  • Monitor security advisories and vulnerability databases for the specific markup engines used.
  • Consider using markup engines with a strong security track record and active maintenance.
  • Implement input validation to reject overly complex or suspicious markup structures that might trigger engine vulnerabilities.