diff --git a/blockchain/all_challenges/2019/de1ctf/EasyEOS/backend/package.json b/blockchain/all_challenges/2019/de1ctf/EasyEOS/backend/package.json
index c8d6a5d..ae7bee6 100644
--- a/blockchain/all_challenges/2019/de1ctf/EasyEOS/backend/package.json
+++ b/blockchain/all_challenges/2019/de1ctf/EasyEOS/backend/package.json
@@ -13,7 +13,7 @@
     "dotenv": "^8.0.0",
     "eosjs": "^20.0.0",
     "node-fetch": "^2.6.1",
-    "nodemailer": "^6.2.1"
+    "nodemailer": "^6.6.1"
   },
   "devDependencies": {
     "npm-run-all": "^4.1.3"
diff --git a/blockchain/all_challenges/2019/de1ctf/EasyEOS/backend/yarn.lock b/blockchain/all_challenges/2019/de1ctf/EasyEOS/backend/yarn.lock
index ed0bc0e..e550bae 100644
--- a/blockchain/all_challenges/2019/de1ctf/EasyEOS/backend/yarn.lock
+++ b/blockchain/all_challenges/2019/de1ctf/EasyEOS/backend/yarn.lock
@@ -380,10 +380,10 @@ node-fetch@^2.6.1:
   resolved "https://registry.yarnpkg.com/node-fetch/-/node-fetch-2.6.1.tgz#045bd323631f76ed2e2b55573394416b639a0052"
   integrity sha512-V4aYg89jEoVRxRb2fJdAg8FHvI7cEyYdVAh94HH0UIK8oJxUfkjlDQN9RbMx+bEjP7+ggMiFRprSti032Oipxw==
 
-nodemailer@^6.2.1:
-  version "6.2.1"
-  resolved "https://registry.npm.taobao.org/nodemailer/download/nodemailer-6.2.1.tgz#20d773925eb8f7a06166a0b62c751dc8290429f3"
-  integrity sha1-INdzkl6496BhZqC2LHUdyCkEKfM=
+nodemailer@^6.6.1:
+  version "6.6.1"
+  resolved "https://registry.yarnpkg.com/nodemailer/-/nodemailer-6.6.1.tgz#2a05fbf205b897d71bf43884167b5d4d3bd01b99"
+  integrity sha512-1xzFN3gqv+/qJ6YRyxBxfTYstLNt0FCtZaFRvf4Sg9wxNGWbwFmGXVpfSi6ThGK6aRxAo+KjHtYSW8NvCsNSAg==
 
 normalize-package-data@^2.3.2:
   version "2.5.0"