FIX: Gracefully handle inline images in emails (#12855)

lib/email/receiver.rb

@@ -1124,8 +1124,8 @@ module Email
                     raw = raw.sub(match, replacement)
                   end
                 end
-              elsif raw[/\[image:.*?\d+[^\]]*\]/i]
-                raw.sub!(/\[image:.*?\d+[^\]]*\]/i, UploadMarkdown.new(upload).to_markdown)
+              elsif raw[/\[image:[^\]]*\]/i]
+                raw.sub!(/\[image:[^\]]*\]/i, UploadMarkdown.new(upload).to_markdown)
               else
                 raw << "\n\n#{UploadMarkdown.new(upload).to_markdown}\n\n"
               end

spec/components/email/receiver_spec.rb

@@ -585,6 +585,19 @@ describe Email::Receiver do
       MD
     end
 
+    it "gracefully handles malformed images in HTML part" do
+      expect { process(:inline_image_2) }.to change { topic.posts.count }
+
+      post = topic.posts.last
+      upload = post.uploads.last
+
+      expect(post.raw).to eq(<<~MD.chomp)
+      [image:#{'0' * 5000}
+
+      ![#{upload.original_filename}|#{upload.width}x#{upload.height}](#{upload.short_url})
+      MD
+    end
+
     it "supports attached images in signature" do
       SiteSetting.incoming_email_prefer_html = true
       SiteSetting.always_show_trimmed_content = true