GHSA-9h9g-93gc-623h Possible XSS vulnerability with certain configurations of rails-html-sanitizer

• RubyGems rails-html-sanitizer: < 1.4.4 → fixed in 1.4.4

Summary There is a possible XSS vulnerability with certain configurations of Rails::Html::Sanitizer. • Versions affected: ALL • Not affected: NONE • Fixed versions: 1.4.4 Impact A possible XSS vulnerability with certain configurations of Rails::Html::Sanitizer may allow an attacker to inject content if 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 allowed tags are being overridden. Applications may be doing this in four different ways: 1. using application configuration: ```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. using Rails::Html::SafeListSanitizer class method `allowed_tags=`: ```ruby # class-level option Rails::Html::SafeListSanitizer.allowed_tags = ["math", "style"] # or Rails::Html::SafeListSanitizer.allowed_tags = ["svg", "style"] ``` 4. using a `:tags` options to the Rails::Html::SafeListSanitizer instance method `sanitize`: ```ruby # instance-level option Rails::Html::SafeListSanitizer.new.sanitize(@article.body, tags: ["math", "style"]) # or Rails::Html::SafeListSanitizer.new.sanitize(@article.body, 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 immediately. Workarounds Remove "style" from the overridden allowed tags, or remove "math" and "svg" from the overridden allowed tags. References • CWE - CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (4.9) • https://hackerone.com/reports/1656627 Credit This vulnerability was responsibly reported by Dominic Breuker.