FIX: handle invalid tags

app/controllers/tags_controller.rb

@@ -277,10 +277,14 @@ class TagsController < ::ApplicationController
     def construct_url_with(action, opts)
       method = url_method(opts)
 
-      url = if action == :prev
-        public_send(method, opts.merge(prev_page_params(opts)))
-      else # :next
-        public_send(method, opts.merge(next_page_params(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') }