Important Notes:

• Marked the editor.beforePaste event as deprecated.
• The default class of captioned images has changed to image (was: caption). Please note that once edited in CKEditor 4.4+, all existing images of the caption class (<figure class="caption">) will be filtered out unless theconfig.image2_captionedClass option is set to caption. For backward compatibility (i.e. when upgrading), it is highly recommended to use this setting, which also helps prevent CSS conflicts, etc. This does not apply to new CKEditor integrations.
• Widgets without defined buttons are no longer registered automatically to the Advanced Content Filter. Before CKEditor 4.4 widgets were registered to the ACF which was an incorrect behavior (#11567). This change should not have any impact on standard scenarios, but if your button does not execute the widget command, you need to set allowedContent andrequiredContent properties for it manually, because the editor will not be able to find them.
• The Show Borders plugin was added to the Standard installation package in order to ensure that unstyled tables are still visible for the user (#11665).
• Since CKEditor 4.4 the editor instance should be passed to CKEDITOR.style methods to ensure full compatibility with other features (e.g. applying styles to widgets requires that). We ensured backward compatibility though, so the CKEDITOR.style will work even when the editor instance is not provided.

New Features:

• #11297: Styles can now be applied to widgets. The definition of a style which can be applied to a specific widget must contain two additional properties — type and widget. Read more in the Widget Styles section of the "Syles Drop-down" guide. Note that by default, widgets support only classes and no other attributes or styles. Related changes and features:
  • Introduced the CKEDITOR.style.addCustomHandler() method for registering custom style handlers.
  • The CKEDITOR.style.apply() and CKEDITOR.style.remove() methods are now called with an editor instance instead of the document so they can be reused by the CKEDITOR.editor.applyStyle() and CKEDITOR.editor.removeStyle() methods. Backward compatibility was preserved, but from CKEditor 4.4 it is highly recommended to pass an editor instead of a document to these methods.
  • Many new methods and properties were introduced in the Widget API to make the handling of styles by widgets fully customizable. See: widget.definition.styleableElements,  widget.definition.styleToAllowedContentRule,  widget.addClass(),  widget.removeClass(),  widget.getClasses(),  widget.hasClass(),  widget.applyStyle(),  widget.removeStyle(),  widget.checkStyleActive().
  • Integration with the Allowed Content Filter required an introduction of the CKEDITOR.style.toAllowedContent() method which can be implemented by the custom style handler and if exists, it is used by the CKEDITOR.filter to translate a style to allowed content rules.
• #11300: Various changes in the Enhanced Image plugin:
  • Introduced the config.image2_captionedClass option to configure the class of captioned images.
  • Introduced the config.image2_alignClasses option to configure the way images are aligned with CSS classes. If this setting is defined, the editor produces classes instead of inline styles for aligned images.
  • Default image caption can be translated (customized) with the editor.lang.image2.captionPlaceholder string.
• #11341: Enhanced Image plugin: It is now possible to add a link to any image type.
• #10202: Introduced wildcard support in the Allowed Content Rules format.
• #10276: Introduced blacklisting in the Allowed Content Filter.
• #10480: Introduced code snippets with code highlighting. There are two versions available so far — the default Code Snippetwhich uses the highlight.js library and the Code Snippet GeSHi which uses the GeSHi library.
• #11737: Introduced an option to prevent filtering of an element that matches custom criteria (seefilter.addElementCallback()).
• #11532: Introduced the editor.addContentsCss() method that can be used for adding custom CSS files.
• #11536: Added the CKEDITOR.tools.htmlDecode() method for decoding HTML entities.
• #11225: Introduced the CKEDITOR.tools.transparentImageData property which contains transparent image data to be used in CSS or as image source.

Other changes:

• #11377: Unified internal representation of empty anchors using the fake objects.
• #11422: Removed Firefox 3.x, Internet Explorer 6 and Opera 12.x leftovers in code.
• #5217: Setting data (including switching between modes) creates a new undo snapshot. Besides that:
  • Introduced the editable.status property.
  • Introduced a new forceUpdate option for the editor.lockSnapshot event.
  • Fixed: Selection not being unlocked in inline editor after setting data (#11500).
• The WebSpellChecker plugin was updated to the latest version.

Fixed Issues:

• #10190: Fixed: Removing block style with editor.removeStyle() should result in a paragraph and not a div.
• #11727: Fixed: The editor tries to select a non-editable image which was clicked.

Fixed Issues:

• #11597: [IE11] Fixed: Error thrown when trying to open the preview using the keyboard.
• #11544: Placeholders will no longer be upcasted in parents not accepting <span> elements.
• #8663: Fixed element.renameNode() not clearing the element.getName() cache.
• #11574: Fixed: Backspace destroying the DOM structure if an inline editable is placed in a list item.
• #11603: Fixed: Table Resize attaches to tables outside the editable.
• #9205, #7805, #8216: Fixed: {cke_protected_*} appearing in data in various cases where HTML comments are placed next to " or '.
• #11635: Fixed: Some attributes are not protected before the content is passed through the fix bin.
• #11660: [IE] Fixed: Table content is lost when some extra markup is inside the table.
• #11641: Fixed: Switching between modes in the classic editor removes content styles for the inline editor.
• #11568: Fixed: Styles drop-down list is not enabled on selection change.