Filter out old system notes for epics

app/controllers/concerns/issuable_actions.rb

@@ -110,7 +110,7 @@ module IssuableActions
     end
 
     notes = prepare_notes_for_rendering(notes)
-    notes = notes.reject { |n| n.cross_reference_not_visible_for?(current_user) }
+    notes = notes.select { |n| n.visible_for?(current_user) }
 
     discussions = Discussion.build_collection(notes, issuable)
 

app/controllers/concerns/notes_actions.rb

@@ -29,7 +29,7 @@ module NotesActions
     end
 
     notes = prepare_notes_for_rendering(notes)
-    notes = notes.reject { |n| n.cross_reference_not_visible_for?(current_user) }
+    notes = notes.select { |n| n.visible_for?(current_user) }
 
     notes_json[:notes] =
       if use_note_serializer?

app/models/note.rb

@@ -331,6 +331,10 @@ class Note < ApplicationRecord
     cross_reference? && !all_referenced_mentionables_allowed?(user)
   end
 
+  def visible_for?(user)
+    !cross_reference_not_visible_for?(user)
+  end
+
   def award_emoji?
     can_be_award_emoji? && contains_emoji_only?
   end

changelogs/unreleased/security-epic-notes-api-reveals-historical-info-ce-master.yml

@@ -0,0 +1,5 @@
+---
+title: Filter out old system notes for epics in notes api endpoint response
+merge_request:
+author:
+type: security

lib/api/discussions.rb

@@ -239,7 +239,7 @@ module API
         # because notes are redacted if they point to projects that
         # cannot be accessed by the user.
         notes = prepare_notes_for_rendering(notes)
-        notes.reject { |n| n.cross_reference_not_visible_for?(current_user) }
+        notes.select { |n| n.visible_for?(current_user) }
       end
       # rubocop: enable CodeReuse/ActiveRecord
     end

lib/api/helpers/notes_helpers.rb

@@ -12,7 +12,7 @@ module API
       end
 
       def update_note(noteable, note_id)
-        note = noteable.notes.find(params[:note_id])
+        note = noteable.notes.find(note_id)
 
         authorize! :admin_note, note
 
@@ -61,8 +61,8 @@ module API
       end
 
       def get_note(noteable, note_id)
-        note = noteable.notes.with_metadata.find(params[:note_id])
-        can_read_note = !note.cross_reference_not_visible_for?(current_user)
+        note = noteable.notes.with_metadata.find(note_id)
+        can_read_note = note.visible_for?(current_user)
 
         if can_read_note
           present note, with: Entities::Note

lib/api/notes.rb

@@ -42,7 +42,7 @@ module API
           # array returned, but this is really a edge-case.
           notes = paginate(raw_notes)
           notes = prepare_notes_for_rendering(notes)
-          notes = notes.reject { |n| n.cross_reference_not_visible_for?(current_user) }
+          notes = notes.select { |note| note.visible_for?(current_user) }
           present notes, with: Entities::Note
         end
         # rubocop: enable CodeReuse/ActiveRecord