http://stackoverflow.com/questions/39042006/how-to-invalidate-inputs-internal-state

components.my-component.js

import Ember from 'ember';
const {get,set} = Ember;
export default Ember.Component.extend({
  val:'',
  actions:{
    update(newVal){      
      let oldVal = get(this, 'val');      
      console.log('newVal-',newVal+' oldVal-',oldVal);
      if(!newVal.includes('C')) {
            set(this, 'val', newVal);
        } else {          
          this.$('#fieldId').val(oldVal);
        }
    }
  }
});

controllers.application.js

import Ember from 'ember';
const {get,set} = Ember;

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  val:'',
  actions:{
    update(newVal){      
      let oldVal = get(this, 'val');      
      console.log('newVal-',newVal+' oldVal-',oldVal);
      set(this, 'val', newVal);
      if(newVal.includes('C')) {        
          Ember.run.schedule('afterRender', () => {             
        			this.set('val', oldVal);
      			});
        } 
    }
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
{{my-component }}
<br>
{{outlet}}
<br>
<br>

templates.components.my-component.hbs

<input id='fieldId' name='fieldName' value={{val}} oninput={{action 'update' value='target.value'}} />
{{val}}
{{yield}}

twiddle.json

{
  "version": "0.10.4",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.7.0",
    "ember-data": "2.7.0",
    "ember-template-compiler": "2.7.0"
  },
  "addons": {}
}