html.security.audit.eval-detected.eval-detected

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Detected the use of eval(...). This can introduce a Cross-Site-Scripting (XSS) vulnerability if this comes from user-provided input. Follow OWASP best practices to ensure you handle XSS within a JavaScript context correct, and consider using safer APIs to evaluate user-input such as JSON.parse(...).

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Defintion

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rules:
  - id: eval-detected
    message: "Detected the use of eval(...). This can introduce  a
      Cross-Site-Scripting (XSS) vulnerability if this  comes from user-provided
      input. Follow OWASP best  practices to ensure you handle XSS within a
      JavaScript context correct, and consider using safer APIs to
      evaluate  user-input such as JSON.parse(...). "
    metadata:
      cwe:
        - "CWE-79: Improper Neutralization of Input During Web Page Generation
          ('Cross-site Scripting')"
      owasp:
        - A07:2017 - Cross-Site Scripting (XSS)
        - A03:2021 - Injection
      category: security
      technology:
        - browser
      cwe2022-top25: true
      cwe2021-top25: true
      subcategory:
        - audit
      likelihood: LOW
      impact: MEDIUM
      confidence: LOW
      references:
        - https://owasp.org/Top10/A03_2021-Injection
        - https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
      vulnerability_class:
        - Cross-Site-Scripting (XSS)
    languages:
      - html
    severity: WARNING
    patterns:
      - pattern-inside: |
          <script ...>$...A</script>
      - metavariable-pattern:
          metavariable: $...A
          language: javascript
          patterns:
            - pattern-either:
                - pattern: $X(...)
            - pattern-not: $X("...")
            - metavariable-regex:
                metavariable: $X
                regex: ^(eval)$
            - focus-metavariable: $X

Examples

eval-detected.html

<!-- ruleid: eval-detected -->
<script>
    const rootDiv = document.getElementById('root');
    import { sanitize } from "dompurify"
    const hash = location.hash.slice(1)
    
    
    eval(hash1)
    
    const obj2 = { foo: 'baz', y: hash1 };
    
    const clonedObj = { ...obj2 };
    
    eval(clonedObj.y);
    
    // ok: eval-detected
    eval("safe");
    
    
    
    </script>