Disallow the `name` attribute on all user-provided markup

A malicious user was able to do something like

    <img src="" name="getElementById">

to override the `document.getElementById` method, which would result in
JavaScript errors being thrown.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/36104

app/views/projects/blob/viewers/_route_map.html.haml

@@ -6,4 +6,4 @@
   This Route Map is invalid:
   = viewer.validation_message
 
-= link_to 'Learn more', help_page_path('ci/environments', anchor: 'route-map')
+= link_to 'Learn more', help_page_path('ci/environments', anchor: 'go-directly-from-source-files-to-public-pages-on-the-environment')

app/views/projects/blob/viewers/_route_map_loading.html.haml

 = icon('spinner spin fw')
 Validating Route Map…
 
-= link_to 'Learn more', help_page_path('ci/environments', anchor: 'route-map')
+= link_to 'Learn more', help_page_path('ci/environments', anchor: 'go-directly-from-source-files-to-public-pages-on-the-environment')

changelogs/unreleased/rs-issue-36104.yml

+---
+title: Disallow the `name` attribute on all user-provided markup
+merge_request:
+author:

doc/ci/environments.md

@@ -448,8 +448,7 @@ and/or `production`) you can see this information in the merge request itself.
 
 ![Environment URLs in merge request](img/environments_link_url_mr.png)
 
-### <a name="route-map"></a>Go directly from source files to public pages on the environment
-
+### Go directly from source files to public pages on the environment
 
 > Introduced in GitLab 8.17.
 

doc/install/database_mysql.md

@@ -75,7 +75,7 @@ log_bin_trust_function_creators=1
 
 ### MySQL utf8mb4 support
 
-After installation or upgrade, remember to [convert any new tables](#convert) to `utf8mb4`/`utf8mb4_general_ci`.
+After installation or upgrade, remember to [convert any new tables](#tables-and-data-conversion-to-utf8mb4) to `utf8mb4`/`utf8mb4_general_ci`.
 
 ---
 
@@ -230,7 +230,6 @@ We need to check, enable and probably convert your existing GitLab DB tables to
 > Now, ensure that [innodb_file_format](https://dev.mysql.com/doc/refman/5.6/en/tablespace-enabling.html) and [innodb_large_prefix](http://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_large_prefix) are **persisted** in your `my.cnf` file.
 
 #### Tables and data conversion to utf8mb4
-<a name="convert"></a>
 
 Now that you have a persistent MySQL setup, you can safely upgrade tables after setup or upgrade time:
 

lib/banzai/filter/sanitization_filter.rb

@@ -43,6 +43,9 @@ module Banzai
         whitelist[:elements].push('abbr')
         whitelist[:attributes]['abbr'] = %w(title)
 
+        # Disallow `name` attribute globally
+        whitelist[:attributes][:all].delete('name')
+
         # Allow any protocol in `a` elements...
         whitelist[:protocols].delete('a')
 

spec/features/copy_as_gfm_spec.rb

@@ -288,8 +288,6 @@ describe 'Copy as GFM', js: true do
         'SanitizationFilter',
 
         <<-GFM.strip_heredoc
-        <a name="named-anchor"></a>
-
         <sub>sub</sub>
 
         <dl>

spec/lib/banzai/filter/sanitization_filter_spec.rb

@@ -87,6 +87,18 @@ describe Banzai::Filter::SanitizationFilter do
       expect(filter(act).to_html).to eq exp
     end
 
+    it 'disallows the `name` attribute globally' do
+      html = <<~HTML
+        <img name="getElementById" src="">
+        <span name="foo" class="bar">Hi</span>
+      HTML
+
+      doc = filter(html)
+
+      expect(doc.at_css('img')).not_to have_attribute('name')
+      expect(doc.at_css('span')).not_to have_attribute('name')
+    end
+
     it 'allows `summary` elements' do
       exp = act = '<summary>summary line</summary>'
       expect(filter(act).to_html).to eq exp