WordPress 4.8 “Evans” released last month and it introduced TinyMCE functionality to the Text widget. However, it caused issues for those who use Custom HTML as the Visual editor often removes the portions of the code.
WordPress 4.8 Beta 1 has now solved this problem by including a dedicated custom HTML widget and is available for testing.
Weston Ruter said, “For advanced users or any user who needs to paste in HTML snippets, there is now a dedicated ‘Custom HTML’ widget that is especially for adding arbitrary HTML to your sidebar.”
He added, “This widget will retain the application of the widget_text filters, in addition to having a new dedicated widget_custom_html_content filter.”
“For use cases that involve adding content to your sidebar, the Text widget will continue to feature the same Visual editing interface that the post editor has (TinyMCE).”
The users who access Text widgets that have Custom HTML in WordPress 4.8 Beta 1, will now see a note at the top of the widget suggesting to use the Custom HTML widget.
Users will now be suggested to use the Text tab or use the Custom HTML widget if they paste or type HTML into a text widget with the Visual editor active.
The Custom HTML widget is same as Text widget in the previous version of WordPress—WordPress 4.7.
Websites that already have Text widgets with custom HTML that might be modified by the Visual editor are opened in a legacy mode.
Legacy mode keeps the old Text widget interface, including the check box on whether or not to automatically add paragraphs. This will prevent the Visual editor from altering the code.
Ruter said that the ideal way to test these improvements is to install it on a staging site that has Text widgets containing HTML and is known to be problematic in WordPress 4.8. After upgrading, check to see if the widgets open in legacy mode.
WordPress 4.8.1 has been scheduled for release on 1 August. If you encounter any bugs or error, make sure you report them in the WordPress Alpha/Beta section of the support forums.
Reference: WP Tavern