python.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
    mode: taint
    pattern-sources:
      - patterns:
          - pattern: event
          - pattern-inside: |
              def $HANDLER(event, context):
                ...
    pattern-sinks:
      - patterns:
          - pattern: $BODY
          - pattern-inside: >
              {..., "headers": {..., "Content-Type": "text/html", ...}, "body":
              $BODY, ... }
    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
      references:
        - https://owasp.org/Top10/A03_2021-Injection
      cwe2022-top25: true
      cwe2021-top25: true
      subcategory:
        - vuln
      likelihood: HIGH
      impact: MEDIUM
      confidence: MEDIUM
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
      vulnerability_class:
        - Cross-Site-Scripting (XSS)
    languages:
      - python
    severity: WARNING

Examples

tainted-html-response.py

def lambda_handler(event, context):
	html = f"<div>{event['input']}</div>"

	foo = {
		# ok: tainted-html-response
		"data": event['foo']
	}
	bar(foo)

	result = {
		"statusCode": 200,
		# ruleid: tainted-html-response
		"body": html,
		"headers": {
			"Content-Type": "text/html"
		}
	}
	return result