FIX: handle invalid tags

app/controllers/tags_controller.rb

@@ -277,11 +277,15 @@ class TagsController < ::ApplicationController
     def construct_url_with(action, opts)
       method = url_method(opts)
 
+      begin
         url = if action == :prev
           public_send(method, opts.merge(prev_page_params(opts)))
         else # :next
           public_send(method, opts.merge(next_page_params(opts)))
         end
+      rescue
+        raise Discourse::NotFound
+      end
       url.sub('.json?', '?')
     end
 

spec/requests/tags_controller_spec.rb

@@ -50,6 +50,22 @@ describe TagsController do
     end
   end
 
+  describe '#show' do
+    before do
+      Fabricate(:tag, name: 'test')
+    end
+
+    it "should return the right response" do
+      get "/tags/test"
+      expect(response).to be_success
+    end
+
+    it "should handle invalid tags" do
+      get "/tags/%2ftest%2f"
+      expect(response.status).to eq(404)
+    end
+  end
+
   describe '#check_hashtag' do
     let(:tag) { Fabricate(:tag, name: 'test') }