diff --git a/node_modules/y18n/CHANGELOG.md b/node_modules/y18n/CHANGELOG.md
index c259076ad..a3d5bcd53 100644
--- a/node_modules/y18n/CHANGELOG.md
+++ b/node_modules/y18n/CHANGELOG.md
@@ -2,6 +2,13 @@
 
 All notable changes to this project will be documented in this file. See [standard-version](https://github.com/conventional-changelog/standard-version) for commit guidelines.
 
+
+### 4.0.1 (2020-11-30)
+
+### Bug Fixes
+
+* address prototype pollution issue ([#108](https://www.github.com/yargs/y18n/issues/108)) ([a9ac604](https://www.github.com/yargs/y18n/commit/a9ac604abf756dec9687be3843e2c93bfe581f25))
+
 <a name="4.0.0"></a>
 # [4.0.0](https://github.com/yargs/y18n/compare/v3.2.1...v4.0.0) (2017-10-10)
 
diff --git a/node_modules/y18n/index.js b/node_modules/y18n/index.js
index d72068162..727362aac 100644
--- a/node_modules/y18n/index.js
+++ b/node_modules/y18n/index.js
@@ -11,7 +11,7 @@ function Y18N (opts) {
   this.fallbackToLanguage = typeof opts.fallbackToLanguage === 'boolean' ? opts.fallbackToLanguage : true
 
   // internal stuff.
-  this.cache = {}
+  this.cache = Object.create(null)
   this.writeQueue = []
 }
 
diff --git a/node_modules/y18n/package.json b/node_modules/y18n/package.json
index 57f8da1ad..7b2b78312 100644
--- a/node_modules/y18n/package.json
+++ b/node_modules/y18n/package.json
@@ -1,6 +1,6 @@
 {
   "name": "y18n",
-  "version": "4.0.0",
+  "version": "4.0.1",
   "description": "the bare-bones internationalization library used by yargs",
   "main": "index.js",
   "scripts": {
diff --git a/package-lock.json b/package-lock.json
index 091288292..50d698b5c 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -4506,9 +4506,9 @@
       "dev": true
     },
     "y18n": {
-      "version": "4.0.0",
-      "resolved": "https://registry.npmjs.org/y18n/-/y18n-4.0.0.tgz",
-      "integrity": "sha512-r9S/ZyXu/Xu9q1tYlpsLIsa3EeLXXk0VwlxqTcFRfg9EhMW+17kbt9G0NrgCmhGb5vT2hyhJZLfDGx+7+5Uj/w==",
+      "version": "4.0.1",
+      "resolved": "https://registry.npmjs.org/y18n/-/y18n-4.0.1.tgz",
+      "integrity": "sha512-wNcy4NvjMYL8gogWWYAO7ZFWFfHcbdbE57tZO8e4cbpj8tfUcwrwqSl3ad8HxpYWCdXcJUCeKKZS62Av1affwQ==",
       "dev": true
     },
     "yargs": {