confluence-plugins/confluence-editor-plugins/confluence-editor-loader/src/main/resources/jscripts/editor-loader.js

editor-loader.js sets the global AJAX timeout for all requests initiated via $.ajax (which is pretty much all of them) to 12 seconds.

If an AJAX call that takes longer than 12 seconds is initiated on any page where the editor is loaded, the client will timeout and abort the request before it completes.

An example of this happening is moving a page with a large hierarchy, this generally takes longer than 12 seconds, and will show an error message before the operation completes.