Widget editables - does not prevent from dropping unsuportted markup

[Marek Lewandowski]

Widget editables - does not prevent from dropping unsuportted markup

since: 4.3 until major

Currently you are able to drop fancy html markup inside content editable. That allows you to put headers, quotes etc. It's caused by browsers builtin drag'n'drop support.

1. open any image2 sample (/samples/plugins/image2/image2.html)
2. make following selection

   [Broadcasting and quotes
   
   Broadcast on live TV to a world-wide audience, Armstrong stepped onto the lunar surface and described the event as:
   
   One small step for [a] man, one giant leap for mankind.]
   

3. drag it into image widgets content editable

Expected result:
Dragging should be either blocked or stripped.

Current result:
All the markup is placed within editable.

Related issues:
#11115 - Widgets are not filtered by ACF when pasting

[Marek Lewandowski]

Sample result

[Marek Lewandowski]

selection