GitHub Security Advisory: GHSA-cfjx-w229-hgx5
Package: rails-html-sanitizer (RUBYGEMS)
Severity: LOW (CVSS 0.0)
CWE: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Vulnerable versions: = 1.6.0
Patched in: 1.6.1

Summary: rails-html-sanitizer has XSS vulnerability with certain configurations

Details:
## Summary

There is a possible XSS vulnerability with certain configurations of Rails::HTML::Sanitizer 1.6.0 when used with Rails >= 7.1.0.

* Versions affected: 1.6.0
* Not affected: < 1.6.0
* Fixed versions: 1.6.1

## Impact

A possible XSS vulnerability with certain configurations of Rails::HTML::Sanitizer may allow an attacker to inject content if HTML5 sanitization is enabled and the application developer has overridden the sanitizer's allowed tags in the following way:

- the "math", "mtext", "table", and "style" elements are allowed
- and either "mglyph" or "malignmark" are allowed

Code is only impacted if Rails is configured to use HTML5 sanitization, please see documentation for [`config.action_view.sanitizer_vendor`](https://guides.rubyonrails.org/configuring.html#config-action-view-sanitizer-vendor) and [`config.action_text.sanitizer_vendor`](https://guides.rubyonrails.org/configuring.html#config-action-text-sanitizer-vendor) for more information on these configuration options.

The default configuration is to disallow all of these elements except for "table". Code is only impacted if allowed tags are being overridden. Applications may be doing this in a few different ways:

1. using application configuration to configure Action View sanitizers' allowed tags:

  ```ruby
  # In config/application.rb
  config.action_view.sanitized_allowed_tags = ["math", "mtext", "table", "style", "mglyph"]
  # or
  config.action_view.sanitized_allowed_tags = ["math", "mtext", "table", "style", "malignmark"]
  ```

  see https://guides.rubyonrails.org/configuring.html#configuring-action-view

2. using a `:tags` option to the Action View helper `sanitize`:

  ```
  <%= sanitize @comment.body, tags: ["math", "mtext", "table", "style", "mglyph"] %>
  <%# or %>
  <%= sanitize @comment.body, tags: ["math", "mtext", "table", "style", "malignmark"] %>
  ```

  see https://api.rubyonrails.org/classes/ActionView/Helpers/SanitizeHelper.html#method-i-sanitize

3. setting Rails::HTML5::SafeListSanitizer class attribute `allowed_tags`:

  ```ruby
  # class-level option
  Rails::HTML5::SafeListSanitizer.allowed_tags = ["math", "mtext", "table", "style", "mglyph"]
  # or
  Rails::HTML5::SafeListSanitizer.allowed_tags = ["math", "mtext", "table", "style", "malignmark"]
  ```

  (note that this class may also be referenced as `Rails::Html::SafeListSanitizer`)

4. using a `:tags` options to the Rails::HTML5::SafeListSanitizer instance method `sanitize`:

  ```ruby
  # instance-level option
  Rails::HTML5::SafeListSanitizer.new.sanitize(@article.body, tags: ["math", "mtext", "table", "style", "mglyph"])
  # or
  Rails::HTML5::SafeListSanitizer.new.sanitize(@article.body, tags: ["math", "mtext", "table", "style", "malignmark"])
  ```

  (note that this class may also be referenced as `Rails::Html::SafeListSanitizer`)

5. setting ActionText::ContentHelper module attribute `allowed_tags`:

  ```ruby
  ActionText::ContentHelper.allowed_tags = ["math", "mtext", "table", "styl