rails-html-sanitizer is responsible for sanitizing HTML fragments in Rails applications. Prior to version 1.4.4, 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. . This issue is fixed in version 1.4.4. All users overriding the allowed tags to include "math" or "svg" and "style" should either upgrade or use the following workaround immediately: Remove "style" from the overridden allowed tags, or remove "math" and "svg" from the overridden allowed tags.