Fix #5799

src/client/components/post-form.vue

@@ -386,6 +386,7 @@ export default Vue.extend({
 		},
 
 		applyVisibility(v: string) {
+			if (!['public', 'home', 'followers', 'specified'].includes(v)) v = 'public'; // v11互換性のため
 			this.visibility = v;
 		},