On January 10, 2022, we disabled the Free version of WebSpellChecker (WSC) in a dialog that was provided as a plugin, integrated by default into CKEditor 4 editor. This is the end-of-life of this product. Users that have added the WSC plugin to the CKEditor config.js file using the extraPlugins parameter or still using CKEditor lower than 4.16.0 may face an issue with the loading spinner.

To remove the WSC plugin from CKEditor 4, add the following line to your CKEditor config.js file:

config.removePlugins ='wsc';

Note, that the WebSpellChecker Dialog plugin for CKEditor 4 for Drupal 8 was also deprecated. But still, you can use the SCAYT module instead https://www.drupal.org/project/ckeditor_scayt. Also, you can use WProofreader SDK instead. It's not a native module for Drupal, it is a pre-built JavaScript component that can be added to the Drupal pages with the editor (where the spell check is needed).