FIX: multisite upload urls must have either db name or the word 'short-url'.

app/models/post.rb

@@ -886,8 +886,9 @@ class Post < ActiveRecord::Base
   end
 
   def each_upload_url(fragments: nil, include_local_upload: true)
+    current_db = RailsMultisite::ConnectionManagement.current_db
     upload_patterns = [
-      /\/uploads\/#{RailsMultisite::ConnectionManagement.current_db}\//,
+      /\/uploads\/#{current_db}\//,
       /\/original\//,
       /\/optimized\//,
       /\/uploads\/short-url\/[a-zA-Z0-9]+(\.[a-z0-9]+)?/
@@ -898,6 +899,7 @@ class Post < ActiveRecord::Base
 
     links.each do |src|
       next if src.blank? || upload_patterns.none? { |pattern| src.split("?")[0] =~ pattern }
+      next if Rails.configuration.multisite && src.exclude?(current_db) && src.exclude?("short-url")
 
       src = "#{SiteSetting.force_https ? "https" : "http"}:#{src}" if src.start_with?("//")
       next unless Discourse.store.has_been_uploaded?(src) || (include_local_upload && src =~ /\A\/[^\/]/i)

spec/multisite/post_spec.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Multisite Post', type: :multisite do
+  describe '#each_upload_url' do
+    let(:upload1) { Fabricate(:upload_s3) }
+    let(:upload2) { Fabricate(:upload_s3) }
+    let(:upload3) { Fabricate(:upload_s3) }
+
+    it "correctly identifies all upload urls" do
+      SiteSetting.enable_s3_uploads = true
+      SiteSetting.s3_upload_bucket = "s3-upload-bucket"
+      SiteSetting.s3_access_key_id = "some key"
+      SiteSetting.s3_secret_access_key = "some secret key"
+      SiteSetting.s3_cdn_url = "https://cdn.s3.amazonaws.com"
+
+      upload3.url.sub!(RailsMultisite::ConnectionManagement.current_db, "secondsite")
+      upload3.save!
+
+      urls = []
+      post = Fabricate(:post, raw: "A post with image and link upload.\n\n![](#{upload1.short_path})\n\n<a href='#{upload2.url}'>Link to upload</a>\n![](#{upload3.url})")
+      post.each_upload_url { |src, _, _| urls << src.sub("http:", "") }
+      expect(urls).to eq([upload1.short_path, upload2.url])
+    end
+  end
+end