Post image_count doesn't count favicons and thumbnails in oneboxes, so visitors can post links that get oneboxed

app/models/post.rb

@@ -90,7 +90,7 @@ class Post < ActiveRecord::Base
   end
 
   def self.white_listed_image_classes
-    @white_listed_image_classes ||= ['avatar']
+    @white_listed_image_classes ||= ['avatar', 'favicon', 'thumbnail']
   end
 
   def image_count

spec/models/post_spec.rb

@@ -88,6 +88,8 @@ describe Post do
     let(:post_one_image) { Fabricate.build(:post, post_args.merge(raw: "![sherlock](http://bbc.co.uk/sherlock.jpg)", user: visitor)) }
     let(:post_two_images) { Fabricate.build(:post, post_args.merge(raw: "<img src='http://discourse.org/logo.png'> <img src='http://bbc.co.uk/sherlock.jpg'>", user: visitor)) }
     let(:post_with_avatars) { Fabricate.build(:post, post_args.merge(raw: '<img alt="smiley" title=":smiley:" src="/assets/emoji/smiley.png" class="avatar"> <img alt="wink" title=":wink:" src="/assets/emoji/wink.png" class="avatar">', user: visitor)) }
+    let(:post_with_favicon) { Fabricate.build(:post, post_args.merge(raw: '<img src="/assets/favicons/wikipedia.png" class="favicon">', user: visitor)) }
+    let(:post_with_thumbnail) { Fabricate.build(:post, post_args.merge(raw: '<img src="/assets/emoji/smiley.png" class="thumbnail">', user: visitor)) }
     let(:post_with_two_classy_images) { Fabricate.build(:post, post_args.merge(raw: "<img src='http://discourse.org/logo.png' class='classy'> <img src='http://bbc.co.uk/sherlock.jpg' class='classy'>", user: visitor)) }
 
     it "returns 0 images for an empty post" do
@@ -106,6 +108,14 @@ describe Post do
       post_with_avatars.image_count.should == 0
     end
 
+    it "doesn't count favicons as images" do
+      post_with_favicon.image_count.should == 0
+    end
+
+    it "doesn't count thumbnails as images" do
+      post_with_thumbnail.image_count.should == 0
+    end
+
     it "doesn't count whitelisted images" do
       Post.stubs(:white_listed_image_classes).returns(["classy"])
       post_with_two_classy_images.image_count.should == 0