GHSA-w8gc-x259-rc7x rails-html-sanitize has XSS vulnerability with certain configurations

• RubyGems rails-html-sanitizer: >= 1.6.0, < 1.6.1 → fixed in 1.6.1

Summary There is a possible XSS vulnerability with certain configurations of Rails::HTML::Sanitizer 1.6.0 when used with Rails >= 7.1.0 and Nokogiri = 1.16.8. 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 either of the following ways: • allow both "math" and "style" elements • or allow both "svg" and "style" elements Code is only impacted if Rails is configured to use HTML5 sanitization, please see documentation for `config.action_view.sanitizer_vendor` and `config.action_text.sanitizer_vendor` for more information on these configuration options. 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", "style"] # or config.action_view.sanitized_allowed_tags = ["svg", "style"] ``` see https://guides.rubyonrails.org/configuring.html#configuring-action-view 2. using a `:tags` option to the Action View helper `sanitize`: ``` ``` 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", "style"] # or Rails::HTML5::SafeListSanitizer.allowed_tags = ["svg", "style"] ``` (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", "style"]) # or Rails::HTML5::SafeListSanitizer.new.sanitize(@article.body, tags: ["svg", "style"]) ``` (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", "style"] # or ActionText::ContentHelper.allowed_tags = ["svg", "style"] ``` All users overriding the allowed tags by any of the above mechanisms to include (("math" or "svg") and "style") should either upgrade or use one of the workarounds. Workarounds Any one of the following actions will work around this issue: • Remove "style" from the overridden allowed tags, • Or, remove "math" and "svg" from the overridden allowed tags, • Or, downgrade sanitization to HTML4 (see documentation for `config.action_view.sanitizer_vendor` and `config.action_text.sanitizer_vendor` for more information) • Or, independently upgrade Nokogiri to v1.15.7 or >= 1.16.8. References • CWE - CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (4.9) • Original report: https://hackerone.com/reports/2503220 Credit This vulnerability was responsibly reported by So Sakaguchi (mokusou) and taise.