Browser console warning: "Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check http://xhr.spec.whatwg.org/."

Hello,

When Quickedit is activate I have got this message in the browser console : Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience.
However, the module works well Some users report Quickedit not working at all when they get this warning message.

When I try to find the bug in Quickedit.js, this line is cause of problem :
entityElement.setAttribute('data-quickedit-entity-instance-id', entityInstanceID);

Thanks in advance.