diff --git a/frontend/src/components/ChallengeInfoDialog.vue b/frontend/src/components/ChallengeInfoDialog.vue
index 82f2b1f..f121cd9 100644
--- a/frontend/src/components/ChallengeInfoDialog.vue
+++ b/frontend/src/components/ChallengeInfoDialog.vue
@@ -17,7 +17,7 @@
           class="md-primary md-layout-item card-tag"
           >{{ tag }}</md-chip
         >
-        <div v-if="teamKey && !info.solved" class="flag-field">
+        <div v-if="teamKey && token && !info.solved" class="flag-field">
           <md-field>
             <md-input v-model="flag" :placeholder="flagFormat"></md-input>
           </md-field>
@@ -25,7 +25,7 @@
       </md-dialog-content>
       <md-dialog-actions>
         <md-button
-          v-if="!loading && teamKey && !info.solved"
+          v-if="!loading && teamKey && token && !info.solved"
           class="md-raised md-accent"
           @click="submitFlag"
           >{{ $t("submit") }}</md-button
@@ -56,7 +56,7 @@
 </template>
 
 <script>
-import { mapState } from "vuex";
+import { mapState, mapActions } from "vuex";
 import showdown from "showdown";
 
 import { API } from "@/services/api";
@@ -88,6 +88,13 @@ export default {
     })
   },
   methods: {
+    ...mapActions(["setToken", "setUser", "setRepository"]),
+    handleNeedAuthentication() {
+      this.setToken(null);
+      this.setUser(null);
+      this.setRepository(null);
+      this.showMessage(this.$t("invalidToken"));
+    },
     close() {
       if (this.$route.params.id) {
         this.$router.push("/challenges");
@@ -104,6 +111,7 @@ export default {
       this.loading = true;
       this.sendingFlag = true;
       const nizkctf = new NIZKCTF(
+        this.handleNeedAuthentication,
         this.token,
         this.repository,
         config.submissionsRepo,
diff --git a/frontend/src/internationalization.js b/frontend/src/internationalization.js
index 5aea1e9..cd43907 100644
--- a/frontend/src/internationalization.js
+++ b/frontend/src/internationalization.js
@@ -46,6 +46,7 @@ export default {
     teamCountries: "Team countries",
     submit: "Submit",
     fixErrors: "Please fix the following error(s):",
+    invalidToken: "The github token is invalid. Sign in again",
     teamPrivateKey: "Team private key",
     verifyingFlag: "Please wait, we are checking the flag against the hash.",
     flagFound:
@@ -133,6 +134,7 @@ export default {
     teamCountries: "Países do time",
     submit: "Enviar",
     fixErrors: "Por favor, corrija o(s) seguinte(s) erro(s):",
+    invalidToken: "O token do github está inválido. Faça login novamente",
     teamPrivateKey: "Chave privada do time",
     flagFound:
       "Flag encontrada, enviada! Você pode acompanhar o status do seu envio",
diff --git a/frontend/src/services/nizkctf/github.js b/frontend/src/services/nizkctf/github.js
index 1e7fc4a..8848402 100644
--- a/frontend/src/services/nizkctf/github.js
+++ b/frontend/src/services/nizkctf/github.js
@@ -6,10 +6,18 @@ export const repoNameHandler = repoName => {
 };
 
 export default class GitHub {
-  constructor(token) {
+  constructor(token, onNeedAuthentication) {
     this.octokit = new Octokit({
       auth: token
     });
+
+    this.octokit.hook.error("request", async error => {
+      if (error.status === 401) {
+        onNeedAuthentication();
+      }
+
+      throw error;
+    });
   }
 
   async getUser() {
diff --git a/frontend/src/services/nizkctf/gitlab.js b/frontend/src/services/nizkctf/gitlab.js
index 2c268a1..79969bb 100644
--- a/frontend/src/services/nizkctf/gitlab.js
+++ b/frontend/src/services/nizkctf/gitlab.js
@@ -1,10 +1,11 @@
 import { Gitlab } from "gitlab";
 
 export default class GitLab {
-  constructor(token) {
+  constructor(token, onNeedAuthentication) {
     this.api = new Gitlab({
       oauthToken: token
     });
+    this.onNeedAuthentication = onNeedAuthentication;
   }
 
   async getUser() {
diff --git a/frontend/src/services/nizkctf/index.js b/frontend/src/services/nizkctf/index.js
index 9a6d33c..95b52b0 100644
--- a/frontend/src/services/nizkctf/index.js
+++ b/frontend/src/services/nizkctf/index.js
@@ -8,7 +8,14 @@ import { deployPath } from "../../config";
 const repohostDict = { github: GitHub, gitlab: GitLab };
 
 export default class NIZKCTF {
-  constructor(token, local, upstream, repohost, team = undefined) {
+  constructor(
+    onNeedAuthentication,
+    token,
+    local,
+    upstream,
+    repohost,
+    team = undefined
+  ) {
     if (!repohostDict[repohost]) {
       throw new TypeError(`Invalid repohost: ${repohost}`);
     }
@@ -16,7 +23,7 @@ export default class NIZKCTF {
     this.local = local;
     this.upstream = upstream;
 
-    this.api = new repohostDict[repohost](this.token);
+    this.api = new repohostDict[repohost](this.token, onNeedAuthentication);
     this.team = team;
   }
 
diff --git a/frontend/src/views/AfterLogin.vue b/frontend/src/views/AfterLogin.vue
index 87baaef..95030f5 100644
--- a/frontend/src/views/AfterLogin.vue
+++ b/frontend/src/views/AfterLogin.vue
@@ -20,9 +20,9 @@
         ></md-textarea>
       </md-field>
       <div class="center">
-        <md-button class="md-raised md-primary" @click="copyTeamSecret">
-          {{ $t("copyToClipboard") }}
-        </md-button>
+        <md-button class="md-raised md-primary" @click="copyTeamSecret">{{
+          $t("copyToClipboard")
+        }}</md-button>
       </div>
     </md-content>
     <md-steppers v-else :md-active-step.sync="active" md-vertical md-linear>
@@ -107,17 +107,17 @@
               </md-field>
               <md-list style="height:300px; overflow:scroll">
                 <md-list-item v-for="item in filteredCountries" :key="item.key">
-                  <md-checkbox v-model="team.countries" :value="item.key">{{
-                    item.name
-                  }}</md-checkbox>
+                  <md-checkbox v-model="team.countries" :value="item.key">
+                    {{ item.name }}
+                  </md-checkbox>
                   <country-flag :country="item.key" size="normal" />
                 </md-list-item>
               </md-list>
             </md-content>
             <div style="display:flex; justify-content:center;">
-              <md-button class="md-raised md-primary" type="submit">
-                {{ $t("submit") }}
-              </md-button>
+              <md-button class="md-raised md-primary" type="submit">{{
+                $t("submit")
+              }}</md-button>
             </div>
           </div>
           <div v-else>
@@ -126,9 +126,9 @@
               <md-input v-model="encodedTeamInput" required></md-input>
             </md-field>
             <div style="display:flex; justify-content:center;">
-              <md-button class="md-raised md-primary" type="submit">{{
-                $t("submit")
-              }}</md-button>
+              <md-button class="md-raised md-primary" type="submit">
+                {{ $t("submit") }}
+              </md-button>
             </div>
           </div>
         </form>
@@ -220,6 +220,10 @@ export default {
   },
   methods: {
     ...mapActions(["setToken", "setUser", "setRepository", "setTeam"]),
+    handleNeedAuthentication() {
+      this.setToken(null);
+      this.showMessage(this.$t("invalidToken"));
+    },
     copyTeamSecret() {
       navigator.clipboard
         .writeText(this.encodedTeam)
@@ -288,6 +292,7 @@ export default {
     },
     async createTeam() {
       const nizkctf = new NIZKCTF(
+        this.handleNeedAuthentication,
         this.token,
         this.repository,
         config.submissionsRepo,
@@ -396,7 +401,7 @@ export default {
     },
     async getUser(token) {
       if (config.repohost === "github") {
-        const github = new GitHub(token);
+        const github = new GitHub(token, this.handleNeedAuthentication);
         const data = await github.getUser();
         return data;
       } else if (config.repohost === "gitlab") {
@@ -408,7 +413,7 @@ export default {
     },
     async createFork(token) {
       if (config.repohost === "github") {
-        const github = new GitHub(token);
+        const github = new GitHub(token, this.handleNeedAuthentication);
         const { path } = await github.createFork(config.submissionsRepo);
 
         const branches = await github.listBranches(path);
@@ -443,7 +448,7 @@ export default {
     },
     async verifyFork(token) {
       if (config.repohost === "github") {
-        const github = new GitHub(token);
+        const github = new GitHub(token, this.handleNeedAuthentication);
         const { repo } = repoNameHandler(config.submissionsRepo);
         try {
           const content = await github.getContents(