FIX: Handle malformed URLs in `TopicEmbed.absolutize_urls`.

app/models/topic_embed.rb

@@ -208,14 +208,24 @@ class TopicEmbed < ActiveRecord::Base
     fragment = Nokogiri::HTML5.fragment("<div>#{contents}</div>")
     fragment.css('a').each do |a|
       if a['href'].present?
-        a['href'] = URI.join(prefix, a['href']).to_s
+        begin
+          a['href'] = URI.join(prefix, a['href']).to_s
+        rescue URI::InvalidURIError
+          # NOOP, URL is malformed
+        end
       end
     end
+
     fragment.css('img').each do |a|
       if a['src'].present?
-        a['src'] = URI.join(prefix, a['src']).to_s
+        begin
+          a['src'] = URI.join(prefix, a['src']).to_s
+        rescue URI::InvalidURIError
+          # NOOP, URL is malformed
+        end
       end
     end
+
     fragment.at('div').inner_html
   end
 

spec/models/topic_embed_spec.rb

@@ -379,13 +379,25 @@ describe TopicEmbed do
   end
 
   describe '.absolutize_urls' do
-    let(:invalid_url) { 'http://source.com/#double#anchor' }
-    let(:contents) { "hello world new post <a href='/hello'>hello</a>" }
-
     it "handles badly formed URIs" do
+      invalid_url = 'http://source.com/#double#anchor'
+      contents = "hello world new post <a href='/hello'>hello</a>"
+
       raw = TopicEmbed.absolutize_urls(invalid_url, contents)
       expect(raw).to eq("hello world new post <a href=\"http://source.com/hello\">hello</a>")
     end
+
+    it "handles malformed links" do
+      url = "https://somesource.com"
+
+      contents = <<~CONTENT
+      hello world new post <a href="mailto:somemail@somewhere.org>">hello</a>
+      some image <img src="https:/><invalidimagesrc/">
+      CONTENT
+
+      raw = TopicEmbed.absolutize_urls(url, contents)
+      expect(raw).to eq(contents)
+    end
   end
 
 end