diff --git a/part4/blog-fos/package-lock.json b/part4/blog-fos/package-lock.json
index 3f3a02d..4f2f22c 100644
--- a/part4/blog-fos/package-lock.json
+++ b/part4/blog-fos/package-lock.json
@@ -4622,28 +4622,38 @@
       "integrity": "sha512-vVqVZQyf3WLx2Shd0qJ9xuvqgAyKPLAiqITEtqW0oIUjzo3PePDd6fW9iFz30ef7Ysp/oiWqbhszeGWW2T6Gzw=="
     },
     "mongodb": {
-      "version": "3.6.11",
-      "resolved": "https://registry.npmjs.org/mongodb/-/mongodb-3.6.11.tgz",
-      "integrity": "sha512-4Y4lTFHDHZZdgMaHmojtNAlqkvddX2QQBEN0K//GzxhGwlI9tZ9R0vhbjr1Decw+TF7qK0ZLjQT292XgHRRQgw==",
+      "version": "3.7.3",
+      "resolved": "https://registry.npmjs.org/mongodb/-/mongodb-3.7.3.tgz",
+      "integrity": "sha512-Psm+g3/wHXhjBEktkxXsFMZvd3nemI0r3IPsE0bU+4//PnvNWKkzhZcEsbPcYiWqe8XqXJJEg4Tgtr7Raw67Yw==",
       "requires": {
         "bl": "^2.2.1",
         "bson": "^1.1.4",
         "denque": "^1.4.1",
-        "optional-require": "^1.0.3",
+        "optional-require": "^1.1.8",
         "safe-buffer": "^5.1.2",
         "saslprep": "^1.0.0"
+      },
+      "dependencies": {
+        "optional-require": {
+          "version": "1.1.8",
+          "resolved": "https://registry.npmjs.org/optional-require/-/optional-require-1.1.8.tgz",
+          "integrity": "sha512-jq83qaUb0wNg9Krv1c5OQ+58EK+vHde6aBPzLvPPqJm89UQWsvSuFy9X/OSNJnFeSOKo7btE0n8Nl2+nE+z5nA==",
+          "requires": {
+            "require-at": "^1.0.6"
+          }
+        }
       }
     },
     "mongoose": {
-      "version": "5.13.9",
-      "resolved": "https://registry.npmjs.org/mongoose/-/mongoose-5.13.9.tgz",
-      "integrity": "sha512-JbLw5ie0LJxm7V9LoNxRY//6cyFJf0cOpON2TWUWvF9pabil6ArfECL3xHV2N+mwwO4gXiIa+c0pwTzDUVTgqw==",
+      "version": "5.13.15",
+      "resolved": "https://registry.npmjs.org/mongoose/-/mongoose-5.13.15.tgz",
+      "integrity": "sha512-cxp1Gbb8yUWkaEbajdhspSaKzAvsIvOtRlYD87GN/P2QEUhpd6bIvebi36T6M0tIVAMauNaK9SPA055N3PwF8Q==",
       "requires": {
         "@types/bson": "1.x || 4.0.x",
         "@types/mongodb": "^3.5.27",
         "bson": "^1.1.4",
         "kareem": "2.3.2",
-        "mongodb": "3.6.11",
+        "mongodb": "3.7.3",
         "mongoose-legacy-pluralize": "1.0.2",
         "mpath": "0.8.4",
         "mquery": "3.2.5",
@@ -4704,7 +4714,7 @@
         "ms": {
           "version": "2.0.0",
           "resolved": "https://registry.npmjs.org/ms/-/ms-2.0.0.tgz",
-          "integrity": "sha1-VgiurfwAvmwpAd9fmGF4jeDVl8g="
+          "integrity": "sha512-Tpp60P6IUJDTuOq/5Z8cdskzJujfwqfOTkrwIwj7IRISpnkJnT6SyJ4PCPnGMoFjC9ddhal5KVIYtAt97ix05A=="
         }
       }
     },
@@ -5457,6 +5467,11 @@
       "integrity": "sha1-jcrkcOHIirwtYA//Sndihtp15jc=",
       "dev": true
     },
+    "require-at": {
+      "version": "1.0.6",
+      "resolved": "https://registry.npmjs.org/require-at/-/require-at-1.0.6.tgz",
+      "integrity": "sha512-7i1auJbMUrXEAZCOQ0VNJgmcT2VOKPRl2YGJwgpHpC9CE91Mv4/4UYIUm4chGJaI381ZDq1JUicFii64Hapd8g=="
+    },
     "require-directory": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/require-directory/-/require-directory-2.1.1.tgz",
@@ -5933,7 +5948,7 @@
     "sliced": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/sliced/-/sliced-1.0.1.tgz",
-      "integrity": "sha1-CzpmK10Ewxd7GSa+qCsD+Dei70E="
+      "integrity": "sha512-VZBmZP8WU3sMOZm1bdgTadsQbcscK0UM8oKxKVBs4XAhUo2Xxzm/OFMGBkPusxw9xL3Uy8LrzEqGqJhclsr0yA=="
     },
     "snapdragon": {
       "version": "0.8.2",
@@ -6101,7 +6116,7 @@
     "sparse-bitfield": {
       "version": "3.0.3",
       "resolved": "https://registry.npmjs.org/sparse-bitfield/-/sparse-bitfield-3.0.3.tgz",
-      "integrity": "sha1-/0rm5oZWBWuks+eSqzM004JzyhE=",
+      "integrity": "sha512-kvzhi7vqKTfkh0PZU+2D2PIllw2ymqJKujUcyPMd9Y75Nv4nPbGJZXNhxsgdQab2BmlDct1YnfQCguEvHr7VsQ==",
       "optional": true,
       "requires": {
         "memory-pager": "^1.0.2"
diff --git a/part4/blog-fos/package.json b/part4/blog-fos/package.json
index 1a63d1d..1439c56 100644
--- a/part4/blog-fos/package.json
+++ b/part4/blog-fos/package.json
@@ -25,7 +25,7 @@
     "express": "^4.17.3",
     "express-async-errors": "^3.1.1",
     "jsonwebtoken": "^8.5.1",
-    "mongoose": "^5.12.7",
+    "mongoose": "^5.13.15",
     "mongoose-unique-validator": "^2.0.3"
   }
 }
diff --git a/part4/blog-fos/yarn.lock b/part4/blog-fos/yarn.lock
index 106b1a0..bc66c9a 100644
--- a/part4/blog-fos/yarn.lock
+++ b/part4/blog-fos/yarn.lock
@@ -578,10 +578,10 @@
   dependencies:
     "@babel/types" "^7.3.0"
 
-"@types/bson@*":
-  version "4.0.3"
-  resolved "https://registry.yarnpkg.com/@types/bson/-/bson-4.0.3.tgz#30889d2ffde6262abbe38659364c631454999fbf"
-  integrity sha512-mVRvYnTOZJz3ccpxhr3wgxVmSeiYinW+zlzQz3SXWaJmD1DuL05Jeq7nKw3SnbKmbleW5qrLG5vdyWe/A9sXhw==
+"@types/bson@*", "@types/bson@1.x || 4.0.x":
+  version "4.0.5"
+  resolved "https://registry.yarnpkg.com/@types/bson/-/bson-4.0.5.tgz#9e0e1d1a6f8866483f96868a9b33bc804926b1fc"
+  integrity sha512-vVLwMUqhYJSQ/WKcE60eFqcyuWse5fGH+NMAXHuKrUAPoryq3ATxk5o4bgYNtg5aOM4APVg7Hnb3ASqUYG0PKg==
   dependencies:
     "@types/node" "*"
 
@@ -3594,15 +3594,15 @@ mkdirp@^1.0.3:
   resolved "https://registry.yarnpkg.com/mkdirp/-/mkdirp-1.0.4.tgz#3eb5ed62622756d79a5f0e2a221dfebad75c2f7e"
   integrity sha512-vVqVZQyf3WLx2Shd0qJ9xuvqgAyKPLAiqITEtqW0oIUjzo3PePDd6fW9iFz30ef7Ysp/oiWqbhszeGWW2T6Gzw==
 
-mongodb@3.6.6:
-  version "3.6.6"
-  resolved "https://registry.yarnpkg.com/mongodb/-/mongodb-3.6.6.tgz#92e3658f45424c34add3003e3046c1535c534449"
-  integrity sha512-WlirMiuV1UPbej5JeCMqE93JRfZ/ZzqE7nJTwP85XzjAF4rRSeq2bGCb1cjfoHLOF06+HxADaPGqT0g3SbVT1w==
+mongodb@3.7.3:
+  version "3.7.3"
+  resolved "https://registry.yarnpkg.com/mongodb/-/mongodb-3.7.3.tgz#b7949cfd0adc4cc7d32d3f2034214d4475f175a5"
+  integrity sha512-Psm+g3/wHXhjBEktkxXsFMZvd3nemI0r3IPsE0bU+4//PnvNWKkzhZcEsbPcYiWqe8XqXJJEg4Tgtr7Raw67Yw==
   dependencies:
     bl "^2.2.1"
     bson "^1.1.4"
     denque "^1.4.1"
-    optional-require "^1.0.2"
+    optional-require "^1.1.8"
     safe-buffer "^5.1.2"
   optionalDependencies:
     saslprep "^1.0.0"
@@ -3620,28 +3620,30 @@ mongoose-unique-validator@^2.0.3:
     lodash.foreach "^4.1.0"
     lodash.get "^4.0.2"
 
-mongoose@^5.12.7:
-  version "5.12.7"
-  resolved "https://registry.yarnpkg.com/mongoose/-/mongoose-5.12.7.tgz#9cbf42246c53b7ab79342c04ef72938d4047b071"
-  integrity sha512-BniNwACn7uflK2h+M3juvyLH5nn9JDFgnB5KE2EwWFwSrRyhSpPnCtanRKJW3OtMCJyPccMIjtGZxHNW7JfnIw==
+mongoose@^5.13.15:
+  version "5.13.15"
+  resolved "https://registry.yarnpkg.com/mongoose/-/mongoose-5.13.15.tgz#ba2cd0f22c1a5dd9ae15aaf6b10f03c59a4202dd"
+  integrity sha512-cxp1Gbb8yUWkaEbajdhspSaKzAvsIvOtRlYD87GN/P2QEUhpd6bIvebi36T6M0tIVAMauNaK9SPA055N3PwF8Q==
   dependencies:
+    "@types/bson" "1.x || 4.0.x"
     "@types/mongodb" "^3.5.27"
     bson "^1.1.4"
     kareem "2.3.2"
-    mongodb "3.6.6"
+    mongodb "3.7.3"
     mongoose-legacy-pluralize "1.0.2"
-    mpath "0.8.3"
+    mpath "0.8.4"
     mquery "3.2.5"
     ms "2.1.2"
+    optional-require "1.0.x"
     regexp-clone "1.0.0"
     safe-buffer "5.2.1"
     sift "13.5.2"
     sliced "1.0.1"
 
-mpath@0.8.3:
-  version "0.8.3"
-  resolved "https://registry.yarnpkg.com/mpath/-/mpath-0.8.3.tgz#828ac0d187f7f42674839d74921970979abbdd8f"
-  integrity sha512-eb9rRvhDltXVNL6Fxd2zM9D4vKBxjVVQNLNijlj7uoXUy19zNDsIif5zR+pWmPCWNKwAtqyo4JveQm4nfD5+eA==
+mpath@0.8.4:
+  version "0.8.4"
+  resolved "https://registry.yarnpkg.com/mpath/-/mpath-0.8.4.tgz#6b566d9581621d9e931dd3b142ed3618e7599313"
+  integrity sha512-DTxNZomBcTWlrMW76jy1wvV37X/cNNxPW1y2Jzd4DZkAaC5ZGsm8bfGfNOthcDuRJujXLqiuS6o3Tpy0JEoh7g==
 
 mquery@3.2.5:
   version "3.2.5"
@@ -3888,11 +3890,18 @@ onetime@^5.1.0:
   dependencies:
     mimic-fn "^2.1.0"
 
-optional-require@^1.0.2:
+optional-require@1.0.x:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/optional-require/-/optional-require-1.0.3.tgz#275b8e9df1dc6a17ad155369c2422a440f89cb07"
   integrity sha512-RV2Zp2MY2aeYK5G+B/Sps8lW5NHAzE5QClbFP15j+PWmP+T9PxlJXBOOLoSAdgwFvS4t0aMR4vpedMkbHfh0nA==
 
+optional-require@^1.1.8:
+  version "1.1.8"
+  resolved "https://registry.yarnpkg.com/optional-require/-/optional-require-1.1.8.tgz#16364d76261b75d964c482b2406cb824d8ec44b7"
+  integrity sha512-jq83qaUb0wNg9Krv1c5OQ+58EK+vHde6aBPzLvPPqJm89UQWsvSuFy9X/OSNJnFeSOKo7btE0n8Nl2+nE+z5nA==
+  dependencies:
+    require-at "^1.0.6"
+
 optionator@^0.8.1:
   version "0.8.3"
   resolved "https://registry.yarnpkg.com/optionator/-/optionator-0.8.3.tgz#84fa1d036fe9d3c7e21d99884b601167ec8fb495"
@@ -4317,6 +4326,11 @@ request@^2.88.2:
     tunnel-agent "^0.6.0"
     uuid "^3.3.2"
 
+require-at@^1.0.6:
+  version "1.0.6"
+  resolved "https://registry.yarnpkg.com/require-at/-/require-at-1.0.6.tgz#9eb7e3c5e00727f5a4744070a7f560d4de4f6e6a"
+  integrity sha512-7i1auJbMUrXEAZCOQ0VNJgmcT2VOKPRl2YGJwgpHpC9CE91Mv4/4UYIUm4chGJaI381ZDq1JUicFii64Hapd8g==
+
 require-directory@^2.1.1:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/require-directory/-/require-directory-2.1.1.tgz#8c64ad5fd30dab1c976e2344ffe7f792a6a6df42"