The onclick function does not work in ckeditor

Question

I use CKEditor version 4.5.1, I used CK Editor to view the target and in that I put some onclick function to display some part execution time as

<img onclick="callFun(this)" src="/abc/xyx.gif" /> 

But now that loading content on CKEditor converts my onclick function to

 <img data-cke-saved-src="/abc/xyx.gif" src="/abc/xyx.gif" data-cke-pa-onclick="callFun(this)"> 

As you can see above, it converts my onclick function to data-cke-pa-onclick function.

I create an instance of CKEditor as shown below,

 var editor = CKEDITOR.replace( 'domTextArea',{ allowedContent: true } ); 

I ask you to participate in this. I also tried CKEDITOR - how to add a permanent onclick event? but could not succeed.