diff --git a/docker/exercises/sample_app/Gemfile.lock b/docker/exercises/sample_app/Gemfile.lock
index 02facfa..0c144e4 100644
--- a/docker/exercises/sample_app/Gemfile.lock
+++ b/docker/exercises/sample_app/Gemfile.lock
@@ -73,7 +73,7 @@ GEM
     coffee-script-source (1.12.2)
     concurrent-ruby (1.0.5)
     connection_pool (2.2.2)
-    crass (1.0.4)
+    crass (1.0.6)
     dalli (2.7.8)
     dotenv (2.5.0)
     dotenv-rails (2.5.0)
@@ -98,7 +98,7 @@ GEM
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
       ruby_dep (~> 1.2)
-    loofah (2.2.2)
+    loofah (2.19.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.0)
@@ -107,7 +107,9 @@ GEM
       mimemagic (~> 0.3.2)
     memcachier (0.0.2)
     method_source (0.9.0)
-    mimemagic (0.3.2)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_mime (1.0.1)
     mini_portile2 (2.3.0)
     minitest (5.11.3)
@@ -145,8 +147,8 @@ GEM
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.0.4)
-      loofah (~> 2.2, >= 2.2.2)
+    rails-html-sanitizer (1.4.4)
+      loofah (~> 2.19, >= 2.19.1)
     railties (5.2.1)
       actionpack (= 5.2.1)
       activesupport (= 5.2.1)