Don't use fragment cache on commit page

This makes sure the user viewing the commit does not get to see
anything they're not allowed to see

app/views/projects/commits/_commit.html.haml

@@ -8,19 +8,7 @@
 - ref           = local_assigns.fetch(:ref) { merge_request&.source_branch }
 
 - link = commit_path(project, commit, merge_request: merge_request)
-- cache_key = [project.full_path,
-               ref,
-               commit.id,
-               Gitlab::CurrentSettings.current_application_settings,
-               @path.presence,
-               current_controller?(:commits),
-               merge_request&.iid,
-               view_details,
-               commit.status(ref),
-               I18n.locale].compact
-
-= cache(cache_key, expires_in: 1.day) do
-  %li.commit.flex-row.js-toggle-container{ id: "commit-#{commit.short_id}" }
+%li.commit.flex-row.js-toggle-container{ id: "commit-#{commit.short_id}" }
 
   .avatar-cell.d-none.d-sm-block
     = author_avatar(commit, size: 36, has_tooltip: false)

changelogs/unreleased/security-bvl-exposure-in-commits-list.yml

+---
+title: Don't expose confidential information in commit message list
+merge_request:
+author:
+type: security

spec/features/projects/commits/user_browses_commits_spec.rb

@@ -4,10 +4,9 @@ describe 'User browses commits' do
   include RepoHelpers
 
   let(:user) { create(:user) }
-  let(:project) { create(:project, :repository, namespace: user.namespace) }
+  let(:project) { create(:project, :public, :repository, namespace: user.namespace) }
 
   before do
-    project.add_maintainer(user)
     sign_in(user)
   end
 
@@ -127,6 +126,26 @@ describe 'User browses commits' do
         .and have_selector('entry summary', text: commit.description[0..10].delete("\r\n"))
     end
 
+    context 'when a commit links to a confidential issue' do
+      let(:confidential_issue) { create(:issue, confidential: true, title: 'Secret issue!', project: project) }
+
+      before do
+        project.repository.create_file(user, 'dummy-file', 'dummy content',
+                                       branch_name: 'feature',
+                                       message: "Linking #{confidential_issue.to_reference}")
+      end
+
+      context 'when the user cannot see confidential issues but was cached with a link', :use_clean_rails_memory_store_fragment_caching do
+        it 'does not render the confidential issue' do
+          visit project_commits_path(project, 'feature')
+          sign_in(create(:user))
+          visit project_commits_path(project, 'feature')
+
+          expect(page).not_to have_link(href: project_issue_path(project, confidential_issue))
+        end
+      end
+    end
+
     context 'master branch' do
       before do
         visit_commits_page