mitigations.md

Mitigation Strategies Analysis for adam-p/markdown-here

Mitigation Strategy: Strengthen Sanitization with a Strict Allowlist (Integrated with markdown-here if possible, and supplemented with DOMPurify)

• Description:

  1. Identify Allowed Elements: Determine the absolute minimum set of HTML tags, attributes, and URL schemes required.
  2. Create Allowlist Arrays/Objects: Define these in JavaScript arrays/objects (tags, attributes per tag, URL schemes).
  3. markdown-here Integration (Primary Focus): Explore markdown-here's API documentation thoroughly to find options for customizing allowed tags, attributes, and schemes. Many Markdown libraries offer some level of allowlist configuration. If such options exist, use them to enforce your allowlist directly within markdown-here. This is the most direct markdown-here specific mitigation.
  4. DOMPurify (Secondary, but still important): Even if markdown-here has allowlist capabilities, use DOMPurify after markdown-here rendering as a second layer of defense. Configure DOMPurify with the same allowlist. This handles cases where markdown-here's built-in sanitization might have subtle bypasses.
  5. Prioritize markdown-here's Allowlist: If markdown-here does have allowlist options, use those as your primary sanitization mechanism. DOMPurify becomes a fallback. If markdown-here doesn't have allowlist options, then DOMPurify becomes your primary defense.
  6. Regular Review: Revisit the allowlist regularly.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) - Severity: Critical: Prevents injection of malicious <script> tags, event handlers, and unsafe URL schemes. The direct integration with markdown-here (if possible) is key here.
  • Phishing Attacks - Severity: High: Limits deceptive content creation.
  • Data Exfiltration - Severity: High: Restricts avenues for data leakage.
  • Defacement - Severity: Medium: Prevents major visual alterations.

• Impact:

  • XSS: Risk reduction: Very High (if markdown-here allowlist is used) or High (if only DOMPurify is used).
  • Phishing: Risk reduction: High.
  • Data Exfiltration: Risk reduction: High.
  • Defacement: Risk reduction: Medium.

• Currently Implemented:

  • Examine the code where markdown-here is initialized. Look for configuration options related to sanitization, allowed tags, attributes, or schemes.
  • Check for the existence of allowlist variables used in the markdown-here configuration.
  • Check for DOMPurify usage after markdown-here rendering.

• Missing Implementation:

  • If markdown-here's allowlist capabilities (if they exist) are not being used, this is a critical missing piece. This is the most direct way to mitigate risks within the library.
  • If DOMPurify is not used as a secondary layer, the implementation is less robust.
  • If no allowlist is defined, the implementation relies solely on markdown-here's defaults (insufficient).

Mitigation Strategy: Carefully Configure markdown-here Options (Directly Controlling Behavior)

• Description:

  1. Documentation Review (Focus on Security): Thoroughly review markdown-here's documentation, specifically looking for any options that affect HTML output, sanitization, raw HTML handling, or custom rendering.
  2. Disable Unsafe Options: Explicitly disable any options that could introduce vulnerabilities. This is a direct interaction with markdown-here's configuration. Examples might include options related to:
     • Raw HTML input (if not strictly required).
     • Custom HTML rendering features.
     • Any options that bypass or weaken built-in sanitization.
  3. breaks: false (if feasible): If single line breaks to <br> conversion is not essential, set breaks: false directly within the markdown-here configuration.
  4. Document and Justify: Document each chosen markdown-here option and the security rationale behind it.
  5. Test Configuration Changes: After any modification to markdown-here's options, perform rigorous testing, including attempts to inject malicious Markdown. This is crucial to ensure the configuration is secure.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) - Severity: High: Disabling unsafe options directly within markdown-here prevents specific XSS attack vectors that might be enabled by default or through misconfiguration.
  • Unintended HTML Rendering - Severity: Medium: Reduces the risk of unexpected or undesirable HTML output.

• Impact:

  • XSS: Risk reduction: Medium to High (depending on the specific options disabled). This directly mitigates risks arising from markdown-here's configuration.
  • Unintended HTML Rendering: Risk reduction: Medium.

• Currently Implemented:

  • Examine the code where markdown-here is initialized. Look for an options object or configuration settings being passed to the library.
  • Check if unsafe options are explicitly disabled.
  • Check for documentation explaining the chosen configuration and its security implications.

• Missing Implementation:

  • If markdown-here is used with its default settings without explicit and careful configuration, this is a significant gap. This is a direct failure to use markdown-here securely.
  • If the configuration is not documented, it's difficult to maintain and ensure its security.
  • If thorough testing is not performed after configuration changes, vulnerabilities might be introduced.

Mitigation Strategy: Input Validation (Specifically Before markdown-here Processing)

• Description:

  1. Define Length Limits: Determine reasonable maximum lengths for user input before it reaches markdown-here.
  2. Implement Length Checks: Before passing any input to markdown-here, validate its length. Reject input exceeding the limits. This is a pre-processing step directly related to how markdown-here receives data.
  3. Character Restrictions (Optional, Use with Extreme Caution): If, and only if, the application's use case allows for a very restricted character set, consider implementing restrictions before Markdown processing. This is a supplementary measure and should be used with extreme caution, as it can easily break legitimate Markdown. It's not a replacement for sanitization.
  4. Server-Side Validation: Perform all input validation on the server-side, before calling markdown-here.

• Threats Mitigated:

  • Denial of Service (DoS) - Severity: Medium: Length limits prevent extremely large inputs from overloading markdown-here or consuming excessive resources.
  • Cross-Site Scripting (XSS) - Severity: Low: Character restrictions (if used very carefully) can slightly reduce the XSS attack surface, but they are not a primary defense. Sanitization within and after markdown-here is still essential.

• Impact:

  • DoS: Risk reduction: Medium (protects against resource exhaustion attacks targeting markdown-here).
  • XSS: Risk reduction: Low (a supplementary measure; sanitization is the primary defense).

• Currently Implemented:

  • Check the server-side code that handles user input. Look for length validation and character restriction checks before the input is passed to markdown-here.

• Missing Implementation:

  • If there are no length limits on input before it reaches markdown-here, this is a potential DoS vulnerability.
  • If validation is only performed client-side, it's easily bypassed.