ensure tag/content_tag escapes " in attribute vals

Many helpers mark content as HTML-safe without escaping double quotes -- including `sanitize`. Regardless of whether or not the attribute values are HTML-escaped, we want to be sure they don't include double quotes, as that can cause XSS issues. For example: `content_tag(:div, "foo", title: sanitize('" onmouseover="alert(1);//'))`

CVE-2016-6316

actionview/lib/action_view/helpers/tag_helper.rb

@@ -90,7 +90,7 @@ def tag_option(key, value, escape)
           else
             value = escape ? ERB::Util.unwrapped_html_escape(value) : value
           end
-          %(#{key}="#{value}")
+          %(#{key}="#{value.gsub(/"/, '"'.freeze)}")
         end
 
         private

actionview/test/template/tag_helper_test.rb

@@ -274,6 +274,16 @@ def test_tag_builder_honors_html_safe_with_escaped_array_class
     assert_equal '<p class="song> play&gt;"></p>', tag.p(class: [raw("song>"), "play>"])
   end
 
+  def test_tag_does_not_honor_html_safe_double_quotes_as_attributes
+    assert_dom_equal '<p title="&quot;">content</p>',
+      content_tag('p', "content", title: '"'.html_safe)
+  end
+
+  def test_data_tag_does_not_honor_html_safe_double_quotes_as_attributes
+    assert_dom_equal '<p data-title="&quot;">content</p>',
+      content_tag('p', "content", data: { title: '"'.html_safe })
+  end
+
   def test_skip_invalid_escaped_attributes
     ["&1;", "&#1dfa3;", "& #123;"].each do |escaped|
       assert_equal %(<a href="#{escaped.gsub(/&/, '&amp;')}" />), tag("a", href: escaped)