ruby.rails.security.audit.xss.templates.avoid-content-tag.avoid-content-tag

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'content_tag' exhibits unintuitive escaping behavior and may accidentally expose your application to cross-site scripting. If using Rails 2, only attribute values are escaped. If using Rails 3, content and attribute values are escaped. Tag and attribute names are never escaped. Because of this, it is recommended to use 'html_safe' if you must render raw HTML data.

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Defintion

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rules:
  - id: avoid-content-tag
    message: "'content_tag' exhibits unintuitive escaping behavior and may
      accidentally expose your application to cross-site scripting. If using
      Rails 2, only attribute values are escaped. If using Rails 3, content and
      attribute values are escaped. Tag and attribute names are never escaped.
      Because of this, it is recommended to use 'html_safe' if you must render
      raw HTML data."
    metadata:
      cwe:
        - "CWE-79: Improper Neutralization of Input During Web Page Generation
          ('Cross-site Scripting')"
      source-rule-url: https://brakemanscanner.org/docs/warning_types/content_tag/
      references:
        - https://brakemanscanner.org/docs/warning_types/content_tag/
      category: security
      technology:
        - rails
      owasp:
        - A07:2017 - Cross-Site Scripting (XSS)
        - A03:2021 - Injection
      cwe2022-top25: true
      cwe2021-top25: true
      subcategory:
        - audit
      likelihood: LOW
      impact: MEDIUM
      confidence: LOW
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
    languages:
      - generic
    paths:
      include:
        - "*.erb"
    severity: WARNING
    patterns:
      - pattern-inside: <%= ... %>
      - pattern: content_tag

Examples

avoid-content-tag.erb

@custom_page_title = “Page <strong>Title</strong>”
<div>
  <!-- ruleid: avoid-content-tag -->
  <h1><%= content_tag :p @custom_page_title %></h1>
  <!-- ok: avoid-content-tag -->
  <h1><%= @custom_page_title %></h1>
</div>