feat: Display a security alert

src/App.vue

@@ -225,11 +225,23 @@
                     m.parentNode.insertBefore(o, m)
                 })(document, window, 'https://stats.vanity-eth.tk/tracker.js', 'fathom');
                 fathom('trackPageview');
+            },
+            checkLocation() {
+                try {
+                    this.error = window.self !== window.top ? 'insecure_location' : this.error;
+                } catch (e) {
+                    this.error = 'insecure_location'
+                }
+                const hostname = window.location.hostname;
+                if (hostname && ['localhost', '127.0.0.1', 'vanity-eth.tk'].indexOf(hostname) === -1) {
+                    this.error = 'insecure_location';
+                }
             }
         },
 
         created: function () {
             this.addFavicon();
+            this.checkLocation();
             this.countCores();
             this.initWorkers();
             this.initFathom();

src/css/variables.sass

@@ -15,7 +15,7 @@ $bg-fallback: #09c4c5
 
 $primary: #0cd3bc
 $secondary: #46decc
-$error: #ff839a
+$error: #f55959
 
 $shadow: 1px 5px 10px rgba(0, 0, 0, 0.15)
 $shadow-big: 2px 10px 15px rgba(0, 0, 0, 0.15)

src/vue/Error.vue

@@ -4,6 +4,14 @@
             Your browser does not support multi-thread computation.<br>
             Please use a different browser.
         </p>
+
+        <div v-if="error === 'insecure_location'">
+            <h3>Security alert</h3>
+
+            It seems like you are using Vanity-ETH from an unknown website, which could stole your private key.<br>
+            To stay safe, use Vanity-ETH on <a href="https://vanity-eth.tk">vanity-eth.tk</a>, or download the latest
+            build here<a href="https://git.io/veth-dl" target="_blank">here</a> to use offline.
+        </div>
         <p v-else v-html="error.replace('\n', '<br>')"></p>
     </div>
 </template>
@@ -27,4 +35,5 @@
         color: $text-opposite
         a, a:visited, a:hover
             text-decoration: underline
+            color: $text-opposite
 </style>