Dynamic editor settings. Starting from CKEditor 4.3 Beta, Enter mode values and content filter instances may be changed dynamically (for example when the caret was placed in an element in which editor features should be adjusted). When you are implementing a new editor feature, you should base its behavior on dynamic or staticEnter mode values depending on whether this feature works in selection context or globally on editor content.
"Fake" selection was introduced. It makes it possible to virtually select any element when the real selection remains hidden. See the selection.fake method.
Default htmlParser.filter rules are not applied to non-editable elements (elements with contenteditable attribute set to false and their descendants) anymore. To add a rule which will be applied to all elements you need to pass an additional argument to the filter.addRules method.
Dozens of new methods were introduced – most interesting ones:
#10659: New Enhanced Image plugin that introduces a widget with integrated image captions, an option to center images, and dynamic "click and drag" resizing.
Dropped compatibility support for Internet Explorer 7 and Firefox 3.6.
Both the Basic and the Standard distribution packages will not contain the new Indent Block plugin. Because of this the Advanced Content Filter might remove block indentations from existing contents. If you want to prevent this, either add an appropriate ACF rule to your filter or create a custom build based on the Basic/Standard package and add the Indent Block plugin in CKBuilder.
#10191: Fixed allowed content rules unification, so the filter.allowedContent property always contains rules in the same format.
#10224: Advanced Content Filter does not remove non-empty <a> elements anymore.
Minor issues in plugin integration with Advanced Content Filter:
#10166: Added transformation from the align attribute to float style to preserve backward compatibility after the introduction of Advanced Content Filter.
#10195: Image plugin no longer registers rules for links to Advanced Content Filter.
#9829: Advanced Content Filter - data and features activation based on editor configuration.
Brand new data filtering system that works in 2 modes:
Based on loaded features (toolbar items, plugins) - the data will be filtered according to what the editor in its current configuration can handle.
Based on config.allowedContent rules - the data will be filtered and the editor features (toolbar items, commands, keystrokes) will be enabled if they are allowed.
#9387: Reintroduced Shared Spaces - the ability to display toolbar and bottom editor space in selected locations and to share them by different editor instances.