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rails-html-sanitizer has XSS vulnerability with certain configurations
There is a possible XSS vulnerability with certain configurations of Rails::HTML::Sanitizer 1.6.0 when used with Rails >= 7.1.0.
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:
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.
The default configuration is to disallow all of these elements. Code is only impacted if allowed tags are being overridden. Applications may be doing this in a few different ways:
# In config/application.rb
config.action_view.sanitized_allowed_tags = ["style"]
see https://guides.rubyonrails.org/configuring.html#configuring-action-view
:tags option to the Action View helper sanitize:<%= sanitize @comment.body, tags: ["style"] %>
see https://api.rubyonrails.org/classes/ActionView/Helpers/SanitizeHelper.html#method-i-sanitize
allowed_tags:# class-level option
Rails::HTML5::SafeListSanitizer.allowed_tags = ["style"]
(note that this class may also be referenced as Rails::Html::SafeListSanitizer)
:tags options to the Rails::HTML5::SafeListSanitizer instance method sanitize:# instance-level option
Rails::HTML5::SafeListSanitizer.new.sanitize(@article.body, tags: ["style"])
(note that this class may also be referenced as Rails::Html::SafeListSanitizer)
allowed_tags:ActionText::ContentHelper.allowed_tags = ["style"]
All users overriding the allowed tags by any of the above mechanisms to include "style" and omit "svg" or "math" should either upgrade or use one of the workarounds.
Any one of the following actions will work around this issue:
config.action_view.sanitizer_vendor and config.action_text.sanitizer_vendor for more information).This vulnerability was responsibly reported by So Sakaguchi (mokusou) and taise.
Permalink: https://github.com/advisories/GHSA-2x5m-9ch4-qgrr