diff --git a/components/Account.vue b/components/Account.vue
index 85f48b7c..78109649 100644
--- a/components/Account.vue
+++ b/components/Account.vue
@@ -208,6 +208,7 @@
                     }
 
                     this.$store.commit('setToken', response.token);
+                    this.username = this.$user().username;
                     this.$cookies.set('token', this.$store.state.token, cookieSettings);
                     this.message = 'crud.saved';
                     this.messageIcon = 'check-circle';
diff --git a/server/routes/user.js b/server/routes/user.js
index 856b9240..d14b7a0d 100644
--- a/server/routes/user.js
+++ b/server/routes/user.js
@@ -26,6 +26,8 @@ const isSpam = (email) => {
         || email.length > 128;
 }
 
+const replaceExtension = username => username.replace(/\.(txt|jpg|jpeg|png|pdf|gif|doc|docx|csv)$/i, '_$1');
+
 const saveAuthenticator = async (db, type, user, payload, validForMinutes = null) => {
     const id = ulid();
     await db.get(SQL`INSERT INTO authenticators (id, userId, type, payload, validUntil) VALUES (
@@ -76,10 +78,12 @@ const invalidateAuthenticator = async (db, id) => {
 
 const defaultUsername = async (db, email) => {
     const base = normalise(
-        email.substring(0, email.includes('@') ? email.indexOf('@') : email.length)
-            .padEnd(4, '0')
-            .substring(0, 14)
-            .replace(new RegExp(`[^${USERNAME_CHARS}]`, 'g'), '_')
+        replaceExtension(
+            email.substring(0, email.includes('@') ? email.indexOf('@') : email.length)
+                .padEnd(4, '0')
+                .substring(0, 14)
+                .replace(new RegExp(`[^${USERNAME_CHARS}]`, 'g'), '_')
+        )
     );
 
     const conflicts = (await db.all(SQL`SELECT usernameNorm FROM users WHERE usernameNorm LIKE ${normalise(base) + '%'}`))
@@ -295,6 +299,8 @@ router.post('/user/change-username', handleErrorAsync(async (req, res) => {
         return res.json({ error: 'user.account.changeUsername.invalid' });
     }
 
+    req.body.username = replaceExtension(req.body.username);
+
     const dbUser = await req.db.get(SQL`SELECT * FROM users WHERE usernameNorm = ${normalise(req.body.username)}`);
     if (dbUser && dbUser.id !== req.user.id) {
         return res.json({ error: 'user.account.changeUsername.taken' })