hidden code in blocks

I have a customer who probably have a plugin installed in their browser. When field are edited (notefield and some others) i get alot of space under. When i use firebug i find this code inserted but there are now way to delete it in editing mode. I have to delete the block and so insert it again.

here is the code wich is inserted, found it in firebug.

<grammarly-btn>
<div class="_e725ae-textarea_btn _e725ae-anonymous _e725ae-not_focused" style="visibility: hidden; z-index: 2;" data-reactroot="">
<div class="_e725ae-transform_wrap">
<div title="Protected by Grammarly" class="_e725ae-status"></div>
</div>
</div>
</grammarly-btn>