CVE-2022-23519 (rails-html-sanitizer): Possible XSS vulnerability with certain configurations of rails-html-sanitizer

ADVISORIES

GEM

rails-html-sanitizer

SEVERITY

CVSS v3.x: 6.1 (Medium)

PATCHED VERSIONS

>= 1.4.4

DESCRIPTION

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 = [&quot;math&quot;, &quot;style&quot;]
  # or
  config.action_view.sanitized_allowed_tags = [&quot;svg&quot;, &quot;style&quot;]

see https://guides.rubyonrails.org/configuring.html#configuring-action-view

using a :tags option to the Action View helper sanitize:

  &lt;%= sanitize @comment.body, tags: [&quot;math&quot;, &quot;style&quot;] %&gt;
  &lt;%# or %&gt;
  &lt;%= sanitize @comment.body, tags: [&quot;svg&quot;, &quot;style&quot;] %&gt;

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 = [&quot;math&quot;, &quot;style&quot;]
  # or
  Rails::Html::SafeListSanitizer.allowed_tags = [&quot;svg&quot;, &quot;style&quot;]

using a :tags options to the Rails::Html::SafeListSanitizer instance method sanitize:

  # instance-level option
  Rails::Html::SafeListSanitizer.new.sanitize(@article.body, tags: [&quot;math&quot;, &quot;style&quot;])
  # or
  Rails::Html::SafeListSanitizer.new.sanitize(@article.body, tags: [&quot;svg&quot;, &quot;style&quot;])

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.

RubySec