Aura Component "Avoid unescaped/sanitized content in output"

Hi All,

We got a suggestion from salesforce to " Avoid unescaped/sanitized content in output". The rule says the below code has " Unescaped Attribute Value XSS". How to fix the issue in the underlined code? Please help me. 

<button id="sales-preview" class = "slds-button" onclick="{!c.openPreviewModal}"> <img title ="Preview" height="20" width="20" class="iconSizeClass" src="{!$Resource.TemplateClass + '/Preview.png'}"/> </button>                                                 <button id="sales-edit" class="slds-button" onclick="{!c.openEditModal}">                       <img title ="Edit" height="11" width="13" class="iconSizeClass" src="  {!$Resource.TemplateClass + '/Edit.png'}"/> </button> 

Thanks