Fixed escaping issue with labels filter

Closes #15552

app/assets/javascripts/gl_dropdown.js

@@ -556,7 +556,7 @@
       if (isInput) {
         field = $(this.el);
       } else {
-        field = this.dropdown.parent().find("input[name='" + fieldName + "'][value='" + value + "']");
+        field = this.dropdown.parent().find("input[name='" + fieldName + "'][value='" + escape(value) + "']");
       }
       if (el.hasClass(ACTIVE_CLASS)) {
         el.removeClass(ACTIVE_CLASS);

app/assets/javascripts/labels_select.js

@@ -164,7 +164,7 @@
                 instance.addInput(this.fieldName, label.id);
               }
             }
-            if ($form.find("input[type='hidden'][name='" + ($dropdown.data('fieldName')) + "'][value='" + (this.id(label)) + "']").length) {
+            if ($form.find("input[type='hidden'][name='" + ($dropdown.data('fieldName')) + "'][value='" + escape(this.id(label)) + "']").length) {
               selectedClass.push('is-active');
             }
             if ($dropdown.hasClass('js-multiselect') && removesAll) {

app/views/shared/issuable/_label_dropdown.html.haml

@@ -12,7 +12,7 @@
 - if params[:label_name].present?
   - if params[:label_name].respond_to?('any?')
     - params[:label_name].each do |label|
-      = hidden_field_tag "label_name[]", label, id: nil
+      = hidden_field_tag "label_name[]", u(label), id: nil
 .dropdown
   %button.dropdown-menu-toggle.js-label-select.js-multiselect{class: classes.join(' '), type: "button", data: dropdown_data}
     %span.dropdown-toggle-text

spec/features/issues/filter_issues_spec.rb

@@ -8,6 +8,7 @@ describe 'Filter issues', feature: true do
   let!(:milestone) { create(:milestone, project: project) }
   let!(:label)     { create(:label, project: project) }
   let!(:issue1)    { create(:issue, project: project) }
+  let!(:wontfix)   { create(:label, project: project, title: "Won't fix") }
 
   before do
     project.team << [user, :master]
@@ -107,6 +108,15 @@ describe 'Filter issues', feature: true do
       end
       expect(find('.js-label-select .dropdown-toggle-text')).to have_content(label.title)
     end
+
+    it 'filters by wont fix labels' do
+      find('.dropdown-menu-labels a', text: label.title).click
+      page.within '.labels-filter' do
+        expect(page).to have_content wontfix.title
+        click_link wontfix.title
+      end
+      expect(find('.js-label-select .dropdown-toggle-text')).to have_content(wontfix.title)
+    end
   end
 
   describe 'Filter issues for assignee and label from issues#index' do