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Attack Surface Analysis for bpmn-io/bpmn-js

Attack Surface: 1. Stored/Reflected Cross-Site Scripting (XSS) via BPMN Diagram Content

  • Description: An attacker injects malicious JavaScript code into BPMN diagram elements (e.g., task names, labels, documentation fields, custom properties) within the BPMN XML. When bpmn-js renders this diagram, the injected script executes in the user's browser.
  • How bpmn-js Contributes: bpmn-js is directly responsible for rendering the BPMN diagram content, including user-provided text and attributes from the XML. If bpmn-js does not properly sanitize or escape this content during rendering, it becomes vulnerable to XSS. The library's rendering pipeline is the direct pathway for this vulnerability.
  • Example: A user creates a BPMN diagram and sets the name of a task to <img src=x onerror=alert('XSS')>. When another user views this diagram rendered by bpmn-js, the JavaScript alert('XSS') will execute in their browser.
  • Impact:
    • Cross-Site Scripting (XSS).
    • Session hijacking.
    • Cookie theft.
    • Defacement.
    • Redirection to malicious websites.
  • Risk Severity: High.
  • Mitigation Strategies:
    • Output Encoding/Escaping: Ensure that the application, especially when feeding data to bpmn-js for rendering, properly encodes or escapes user-provided content for the HTML context. This should be done before the data is passed to bpmn-js for display. Use appropriate escaping functions provided by your frontend framework or libraries. While bpmn-js might have some internal sanitization, relying solely on it is not recommended. Application-level output encoding is crucial.
    • Content Security Policy (CSP): Implement a strict Content Security Policy to limit the sources from which the browser is allowed to load resources. This acts as a defense-in-depth measure to mitigate the impact of XSS even if output encoding is missed.

Attack Surface: 2. Dependency Vulnerabilities (Indirectly via bpmn-js)

  • Description: bpmn-js relies on various JavaScript dependencies. Vulnerabilities in these dependencies (both direct and transitive) can indirectly affect the security of applications using bpmn-js. While not a vulnerability in bpmn-js code itself, the library's dependency chain introduces this attack surface.
  • How bpmn-js Contributes: By including bpmn-js in your project, you inherently include its dependency tree. If bpmn-js depends on a vulnerable library, and that vulnerability is exploitable in the context of how bpmn-js or your application uses it, then bpmn-js's dependency choice contributes to the attack surface.
  • Example: A specific version of a library used by bpmn-js (e.g., an XML parsing library or a utility library) is found to have an XSS or Remote Code Execution (RCE) vulnerability. Applications using bpmn-js with this vulnerable dependency are then also at risk.
  • Impact: Varies depending on the nature of the dependency vulnerability. Could range from XSS to RCE.
  • Risk Severity: Medium to High (depending on the severity of the dependency vulnerability - can be Critical for RCE). We are including it here because dependency vulnerabilities can easily become High or Critical.
  • Mitigation Strategies:
    • Regular Dependency Updates: Keep bpmn-js and all its dependencies updated to the latest versions. Regularly check for updates and apply them promptly. This is crucial for mitigating known vulnerabilities in the dependency chain.
    • Dependency Scanning: Use dependency scanning tools (e.g., npm audit, OWASP Dependency-Check, Snyk) to identify known vulnerabilities in your project's dependencies. Integrate these tools into your development and CI/CD pipelines to proactively detect and address vulnerable dependencies introduced by bpmn-js.
    • Vulnerability Monitoring: Subscribe to security advisories and vulnerability databases to stay informed about newly discovered vulnerabilities in libraries you use, including those in bpmn-js's dependency tree.