javascript.aws-lambda.security.tainted-html-response.tainted-html-response

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Detected user input flowing into an HTML response. You may be accidentally bypassing secure methods of rendering HTML by manually constructing HTML and this could create a cross-site scripting vulnerability, which could let attackers steal sensitive user data.

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Defintion

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rules:
  - id: tainted-html-response
    message: Detected user input flowing into an HTML response. You may be
      accidentally bypassing secure methods of rendering HTML by manually
      constructing HTML and this could create a cross-site scripting
      vulnerability, which could let attackers steal sensitive user data.
    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:
        - aws-lambda
      cwe2022-top25: true
      cwe2021-top25: true
      subcategory:
        - vuln
      likelihood: MEDIUM
      impact: MEDIUM
      confidence: MEDIUM
      references:
        - https://owasp.org/Top10/A03_2021-Injection
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
      vulnerability_class:
        - Cross-Site-Scripting (XSS)
    languages:
      - javascript
      - typescript
    severity: WARNING
    mode: taint
    pattern-sources:
      - patterns:
          - pattern-either:
              - pattern-inside: |
                  exports.handler = function ($EVENT, ...) {
                    ...
                  }
              - pattern-inside: |
                  function $FUNC ($EVENT, ...) {...}
                  ...
                  exports.handler = $FUNC
              - pattern-inside: |
                  $FUNC = function ($EVENT, ...) {...}
                  ...
                  exports.handler = $FUNC
          - pattern: $EVENT
    pattern-sinks:
      - patterns:
          - focus-metavariable: $BODY
          - pattern-inside: >
              {..., headers: {..., 'Content-Type': 'text/html', ...}, body:
              $BODY, ... }

Examples

tainted-html-response.js

exports.handler = function (event, context) {
    const html = `<div>${event.name}</div>`;

    const someRandomStuff = {
        // ok: tainted-html-response
        data: event.foo
    }
    bar(someRandomStuff)

    const response = {
        statusCode: 200,
        // ruleid: tainted-html-response
        body: html,
        headers: {
            'Content-Type': 'text/html',
        }
    };

    return response
}