_html translation should escape interpolated arguments

actionpack/CHANGELOG.md

@@ -64,6 +64,20 @@
 
 ## Rails 3.1.2 (unreleased) ##
 
+*   Fix XSS security vulnerability in the `translate` helper method. When using interpolation
+    in combination with HTML-safe translations, the interpolated input would not get HTML
+    escaped. *GH 3664*
+
+    Before:
+
+        translate('foo_html', :something => '<script>') # => "...<script>..."
+
+    After:
+
+        translate('foo_html', :something => '<script>') # => "...&lt;script&gt;..."
+
+    *Sergey Nartimov*
+
 *   Upgrade sprockets dependency to ~> 2.1.0
 
 *   Ensure that the format isn't applied twice to the cache key, else it becomes impossible

actionpack/lib/action_view/helpers/translation_helper.rb

@@ -45,11 +45,16 @@ module ActionView
       # you know what kind of output to expect when you call translate in a template.
       def translate(key, options = {})
         options.merge!(:rescue_format => :html) unless options.key?(:rescue_format)
-        translation = I18n.translate(scope_key_by_partial(key), options)
+        if html_safe_translation_key?(key)
-        if html_safe_translation_key?(key) && translation.respond_to?(:html_safe)
+          html_safe_options = options.dup
-          translation.html_safe
+          options.except(*I18n::RESERVED_KEYS).each do |name, value|
+            html_safe_options[name] = ERB::Util.html_escape(value.to_s)
+          end
+          translation = I18n.translate(scope_key_by_partial(key), html_safe_options)
+
+          translation.respond_to?(:html_safe) ? translation.html_safe : translation
         else
-          translation
+          I18n.translate(scope_key_by_partial(key), options)
         end
       end
       alias :t :translate

actionpack/test/template/translation_helper_test.rb

@@ -17,6 +17,7 @@ class TranslationHelperTest < ActiveSupport::TestCase
         :hello => '<a>Hello World</a>',
         :html => '<a>Hello World</a>',
         :hello_html => '<a>Hello World</a>',
+        :interpolated_html => '<a>Hello %{word}</a>',
         :array_html => %w(foo bar),
         :array => %w(foo bar)
       }
@@ -83,6 +84,11 @@ class TranslationHelperTest < ActiveSupport::TestCase
     assert translate(:'translations.hello_html').html_safe?
   end
 
+  def test_translate_escapes_interpolations_in_translations_with_a_html_suffix
+    assert_equal '<a>Hello &lt;World&gt;</a>', translate(:'translations.interpolated_html', :word => '<World>')
+    assert_equal '<a>Hello &lt;World&gt;</a>', translate(:'translations.interpolated_html', :word => stub(:to_s => "<World>"))
+  end
+
   def test_translation_returning_an_array_ignores_html_suffix
     assert_equal ["foo", "bar"], translate(:'translations.array_html')
   end