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attack-surface.md

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Attack Surface Analysis for ianstormtaylor/slate

Attack Surface: Cross-Site Scripting (XSS) via Custom Elements/Attributes

  • Description: Injection of malicious scripts through improperly handled custom elements and attributes defined within Slate.
    • Slate's Contribution: Slate's core feature of allowing custom elements and attributes provides a direct pathway for XSS if not rigorously controlled. The flexibility, while powerful, increases the attack surface.
    • Example: An attacker creates a custom element named <my-widget> with an attribute data-url intended to load an image. Instead of a URL, they inject javascript:alert('XSS') into the data-url attribute. If the application doesn't sanitize this attribute, the script will execute.
    • Impact: Client-side code execution, session hijacking, data theft, defacement, phishing.
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Strict Whitelisting: Define a strict whitelist of allowed custom elements and attributes. Reject anything not explicitly on the whitelist.
      • Robust Sanitization: Use a battle-tested HTML sanitization library (e.g., DOMPurify) specifically configured for Slate's data model. Sanitize both on input and before rendering. Do not rely solely on Slate's built-in escaping.
      • Content Security Policy (CSP): Implement a strong CSP to limit the sources from which scripts can be executed.
      • Output Encoding: Encode all user-provided data before rendering it in the DOM, even within custom elements.
      • Regular Expression Validation: Use well-crafted regular expressions to validate the format of attribute values (e.g., ensuring a data-url attribute actually contains a valid URL).

Attack Surface: XSS via Plugin Vulnerabilities

  • Description: Exploitation of vulnerabilities within third-party or custom Slate plugins to inject malicious code.
    • Slate's Contribution: Slate's plugin architecture, while enabling extensibility, introduces a significant attack surface. Each plugin is a potential point of failure.
    • Example: A poorly written "image gallery" plugin fails to sanitize image URLs or alt text. An attacker uploads an image with an alt attribute containing a malicious script: <img src="x" alt="innocent image" onerror="alert('XSS')">.
    • Impact: Client-side code execution, session hijacking, data theft, defacement, phishing.
    • Risk Severity: High
    • Mitigation Strategies:
      • Plugin Vetting: Thoroughly review the code of all third-party plugins before integration. Prioritize well-maintained and reputable plugins.
      • Code Review (Custom Plugins): Conduct rigorous code reviews of all custom-built plugins, focusing on input handling and sanitization.
      • Least Privilege: Grant plugins only the minimum necessary permissions within the Slate editor.
      • Regular Updates: Keep all plugins updated to their latest versions to patch security vulnerabilities.
      • Sandboxing (If Feasible): Explore options for sandboxing plugin execution to limit their impact on the main application.

Attack Surface: Data Model Manipulation (JSON Injection)

  • Description: Direct modification of the underlying JSON data model representing the Slate document to inject malicious content or corrupt the document structure.
    • Slate's Contribution: Slate's reliance on a JSON data model means that any vulnerability allowing direct manipulation of this JSON bypasses typical input validation.
    • Example: An attacker compromises an API endpoint used to save the Slate document. They modify the JSON payload to include a malicious script within a text node: {"type": "paragraph", "children": [{"text": "<script>alert('XSS')</script>"}]}.
    • Impact: XSS, data corruption, denial of service.
    • Risk Severity: High
    • Mitigation Strategies:
      • Schema Validation: Implement strict schema validation to ensure the JSON data model conforms to expected types and structures. Reject any invalid JSON.
      • Input Validation (API Level): Treat the JSON data received from any source (API, import, etc.) as untrusted input. Validate it thoroughly before processing.
      • Integrity Checks: Use cryptographic hashing (e.g., SHA-256) to verify the integrity of the JSON data model, especially if it's stored or transmitted.
      • Sanitization (Post-Deserialization): Even after deserializing the JSON, sanitize the resulting Slate nodes before rendering.

Attack Surface: XSS via insertData and Clipboard Handling

  • Description: Injection of malicious code through pasted content that is not properly sanitized.
    • Slate's Contribution: Slate's insertData method and clipboard handling are inherently vulnerable to XSS if pasted content is not rigorously cleaned.
    • Example: A user copies malicious HTML from a compromised website and pastes it into the Slate editor. The HTML contains inline event handlers (e.g., onload, onerror) that execute JavaScript.
    • Impact: Client-side code execution, session hijacking, data theft.
    • Risk Severity: High
    • Mitigation Strategies:
      • Aggressive Sanitization: Use a robust HTML sanitizer (e.g., DOMPurify) configured to remove all potentially dangerous elements and attributes from pasted content.
      • Plain Text Preference: Whenever possible, encourage or enforce plain text pasting to minimize the risk.
      • Custom Paste Handling: Implement custom paste handling logic that intercepts the paste event and performs thorough sanitization before inserting the content into the Slate editor.
      • Cross-Browser Testing: Test clipboard handling across different browsers and operating systems, as their behavior can vary.

Attack Surface: Operational Transformation (OT) Vulnerabilities (Collaborative Editing)

  • Description: Exploitation of flaws in the Operational Transformation (OT) implementation used for collaborative editing to corrupt the document or inject malicious content.
    • Slate's Contribution: If collaborative editing is implemented using Slate and an OT library, vulnerabilities in the OT logic or its integration with Slate can be exploited.
    • Example: An attacker sends malformed OT operations that bypass validation checks and introduce inconsistencies or inject malicious scripts into the document.
    • Impact: Data corruption, XSS, denial of service.
    • Risk Severity: High (if collaborative editing is used)
    • Mitigation Strategies:
      • Vetted OT Library: Use a well-established and thoroughly tested OT library (e.g., ShareDB, Yjs).
      • Operation Validation: Implement rigorous validation of all incoming OT operations on the server-side before applying them to the document.
      • Secure Communication: Use a secure communication channel (e.g., WebSockets over TLS) for transmitting OT operations.
      • Centralized Authority: Consider using a centralized server to manage and validate all OT operations, preventing direct client-to-client manipulation.
      • Conflict Resolution: Implement robust and secure conflict resolution mechanisms.