Rich-Text field in experience editor mode adds unwanted break points in Firefox

Question

When using Firefox for content authoring, when you paste a paragraph of content in your rich text field, it adds unwanted
tags at the end.

I can replicate this issue on the Vanilla instance of Sitecore Version 9.3 and Sitecore Version 10.

Steps to replicate:

1. Open the Content editor
2. Select default home page
3. Select the Text field under Data and click Show editor.
4. Select the content and cut and paste the same (you will not few extra lines added at the bottom)
5. Click Accept in Rich Text Editor
6. Click Edit Html
7. You can now see a new BR tag added <br class="t-last-br"/>

Does anyone know why this happens, it happens only in Firefox. We tried this in Version 9.3 and 10. This may be an issue in other versions too.

Answer 1

We experienced the same issue on a Sitecore 9.3 instance and fixed it adding the following code at the top of the \sitecore\shell\Controls\Rich Text Editor\RichText Commands.js file in our solution, as recommended by the Sitecore Support team:

function RadEditorCustomFilter() {
    RadEditorCustomFilter.initializeBase(this);
    this.set_isDom(false);
    this.set_enabled(true);
    this.set_name("RadEditor filter");
    this.set_description("RadEditor filter description");
}
RadEditorCustomFilter.prototype =
    {
        getHtmlContent: function (content) {
            if (Telerik.Web.Browser.ff) {
                content = content.replace('<br class="t-last-br" />\n', '');
            }
            return content;
        }
    }
RadEditorCustomFilter.registerClass('RadEditorCustomFilter', Telerik.Web.UI.Editor.Filter);

And inside \sitecore\shell\Controls\Rich Text Editor\EditorPage.aspx, inside OnClientLoad add:

var customFilter = new RadEditorCustomFilter();
editor.get_filtersManager().add(customFilter);

Answer 2

I too had faced the similar issue and changing the "HtmlEditor.RemoveScripts" value to "false" fixed it for me. By default, the value for this setting is set to true. This setting is present in Sitecore.Config. The screenshot below for reference: