Summary : I'm assuming that the settings in the WYSIWYG filter of drupal are not adapted by ckeditor-6.x-1.11

Description : I upgraded from drupal module ckeditor-6.x-1.8 (with ckeditor-3.6.2) to drupal module ckeditor-6.x-1.11 (with ckeditor-3.6.3) : replacing the code in the ckeditor module folder by the newer version and running update.php afterwards, I also cleared the cache, just to be sure.
When opening a page in edit mode, all pictures where displayed full-size in the ckeditor window. Upon inspection of the HTML source code in the editor, it turned out that the 'style' attribute of the img tag had been omitted.
When changing the input filter from WYSIWYG to Full HTML, the issue was resolved.
I checked the settings of the WYSIWYG filter and the 'style' attribute is in the allowed list.
When changing back to the original version (ckeditor-6.x-1.8), with the WYSIWYG filter, the page was displayed correctly.