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:
- using application configuration:
# 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
- using a
:tags option to the Action View helper sanitize:
<%= sanitize @comment.body, tags: ["math", "style"] %>
<%# or %>
<%= sanitize @comment.body, tags: ["svg", "style"] %>
see https://api.rubyonrails.org/classes/ActionView/Helpers/SanitizeHelper.html#method-i-sanitize
- using Rails::Html::SafeListSanitizer class method
allowed_tags=:
# class-level option
Rails::Html::SafeListSanitizer.allowed_tags = ["math", "style"]
# or
Rails::Html::SafeListSanitizer.allowed_tags = ["svg", "style"]
- using a
:tags options to the Rails::Html::SafeListSanitizer instance method sanitize:
# 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
Credit
This vulnerability was responsibly reported by Dominic Breuker.
References
Summary
There is a possible XSS vulnerability with certain configurations of Rails::Html::Sanitizer.
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:
Code is only impacted if allowed tags are being overridden. Applications may be doing this in four different ways:
see https://guides.rubyonrails.org/configuring.html#configuring-action-view
:tagsoption to the Action View helpersanitize:see https://api.rubyonrails.org/classes/ActionView/Helpers/SanitizeHelper.html#method-i-sanitize
allowed_tags=::tagsoptions to the Rails::Html::SafeListSanitizer instance methodsanitize: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
Credit
This vulnerability was responsibly reported by Dominic Breuker.
References