Trying to operate with images in RadEditor under IE11 leads to unresponsiveness. For example, using the paragraph style, selecting an image and switching to HTML and Design mode, etc.

You can workaround that by forcing the compatibility mode of the IE to IE8:

<meta http-equiv="X-UA-Compatible" content="IE=8" />

When link is given to any image or text, Unlink command should get enabled. But it gets enabled for text only while remains disabled for images.
http://screencast.com/t/xHgru58pzKL

The issue has been reproducible since 2015 Q1 release

Using plain RadEditor controls with default Default toolbar where ToolProvideID is also used, a JS error is thrown and ToolProvide mechanism does not operate as expected. 

As a temporary workaround, you can use any other toolbar mode (e.g., ShowOnFocus).

The content is not scrolled to the end of the pasted content in IE11 - the scrollbar keeps its initial position instead. The issue is reproducible in IE (tested in IE11) and Chrome, but not in Firefox nor standard editable iframe.

Steps to reproduce:
1. Open in IE: http://demos.telerik.com/aspnet-ajax/editor/examples/overview/defaultcs.aspx
2. Paste big enough content, so the scrollbar will be shown

Actual: The scrollbar stays on the top.
Expected: The content area is scrolled to the end of the pasted content

Possible workaround could be creating a temporary selectable element after the pasted content, which to be selected manually:
		<telerik:RadEditor ID="txtMessage"  runat="server" OnClientPasteHtml="OnClientPasteHtml">
		</telerik:RadEditor>
		<script>
			function OnClientPasteHtml(editor, args) {
				if (args.get_commandName() == "Paste" && $telerik.isIE) {
					args.set_value(args.get_value() + "<div id='selectableEl'></div>");
					setTimeout(function () {
						var selectedEl = editor.get_document().getElementById("selectableEl");
						console.log(editor.getSelectedElement());
						Telerik.Web.UI.Editor.Utils.scrollTo(selectedEl, editor);
						$telerik.$(selectedEl).remove();
					}, 0);
				}
			}
		</script>

Steps to reproduce:
1. Go to the Editor demo page in Chrome
2. CTRL+A on the editor and hit delete
3. Hit Delete or Backspace again
Result: Uncaught TypeError Appears in the console

When EnableComments is set to true, the content from the clipboard is pasted twice in an empty editor.

RadEditor Configuration:

<telerik:RadEditor runat="server"
    EnableComments="true">
    <Tools>
        <telerik:EditorToolGroup>
            <telerik:EditorTool Name="Bold" />
            <telerik:EditorTool Name="Italic" />
            <telerik:EditorTool Name="Underline" />
            <telerik:EditorSeparator />
            <telerik:EditorTool Name="Undo" />
            <telerik:EditorTool Name="Redo" />
            <telerik:EditorTool Name="Cut" />
            <telerik:EditorTool Name="Copy" />
            <telerik:EditorTool Name="Paste" />
            <telerik:EditorTool Name="PastePlainText" Text="Paste Plain Text" />
            <telerik:EditorTool Name="FindAndReplace" Text="Find and Replace" />
            <telerik:EditorSeparator />
            <telerik:EditorTool Name="Indent" />
            <telerik:EditorTool Name="Outdent" />
            <telerik:EditorTool Name="InsertOrderedList" Text="Numbered List" />
            <telerik:EditorTool Name="InsertUnorderedList" Text="Bulleted List" />
            <telerik:EditorTool Name="LinkManager" />
            <telerik:EditorTool Name="Unlink" />
            <telerik:EditorSeparator />
            <telerik:EditorTool Name="AjaxSpellCheck" Text="Spell Check" />
            <telerik:EditorTool Name="InsertSymbol" Text="Insert Symbol" />
        </telerik:EditorToolGroup>
        <telerik:EditorToolGroup>
            <telerik:EditorTool Name="AcceptTrackChange" Text="Accept Change" />
            <telerik:EditorTool Name="RejectTrackChange" Text="Reject Change" />
            <telerik:EditorTool Name="AcceptAllTrackChanges" Text="Accept All Changes" />
            <telerik:EditorTool Name="RejectAllTrackChanges" Text="Reject All Changes" />
            <telerik:EditorTool Name="EnableTrackChangesOverride" Text="Track Changes" />
            <telerik:EditorTool Name="AddComment" Text="Add Comment" />
            <telerik:EditorTool Name="RemoveComment" Text="Remove Comment" />
            <telerik:EditorTool Name="RemoveAllComments" Text="Remove All Comments" />
            <telerik:EditorTool Name="ImageManager" Text="Insert Image" />
        </telerik:EditorToolGroup>
    </Tools>
</telerik:RadEditor>

Potential workaround:
<script type="text/javascript">
    function OnClientPasteHtml(sender, args) {
        var commandName = args.get_commandName();
        var value = args.get_value();
 
        if (commandName == "Paste" && Telerik.Web.Browser.ie) {
            args.set_value(value);
            args.set_cancel(true);
        }
    }
</script>
<telerik:RadEditor runat="server" Height="300px" StripFormattingOptions="Span,Font,Css" EnableTrackChanges="true" OnClientPasteHtml="OnClientPasteHtml"
    ContentFilters="FixEnclosingP,RemoveScripts,FixUlBoldItalic,IECleanAnchors,MozEmStrong,ConvertFontToSpan,ConvertToXhtml,IndentHTMLContent,EncodeScripts,OptimizeSpans,ConvertTags,StripCssExpressions,RemoveExtraBreaks"
    EnableComments="true" NewLineMode="P" EditModes="Design,Html">
</telerik:RadEditor>

Whenever there are texts and text boxes, checking the spelling duplicates the text 
Video reproduction: http://screencast.com/t/oShyk0ww

When I call OnParentNodeChanged on an Editor, while viewing the page using HTTPS, I get the following message in IE:
SEC7111: HTTPS security is compromised by (null) 

When text is pasted in RadEditor with ContentAreaMode="Div" under Firefox and Chrome, the cursor will be positioned before the pasted text.

RadEditor adds redundant nbsps when the cursor is positioned at the beginning of an unordered list and press backspace in IE9

Steps to reproduce:

1. Go to http://demos.telerik.com/aspnet-ajax-beta/editor/examples/overview/defaultcs.aspx

2. Type some text

3. Format it as bold, italic and underline

4. Enter two new empty lines

5. Insert a table

When the height of the RadEditor is too small to accommodate the tools with the given width calling repaint() causes the appearance of the control to break due to incorrect calculations. This means that the control has an optimal (minimal) height.
The repaint() method is automatically called when the control is shown after being initially hidden on the page (e.g. after a partial postback)

Possible workarounds:
- increase the height of the control. For example, 640px width with 264px height and the default set of tools work well
- reduce the number of used tools. Effectively leaves more height for the control to use
- use ToolbarMode=ShowOnFocus to avoid having the tools in the main content initially, they will be shown in a popup when the content area is focused

If the user opens a dialog (Table Wizard, for example) clicking the 'OK' button applies the new changes, but does not close the dialog - it instead loses focus.

The bug is reproduced in all versions of Internet Explorer when RadEditor is configured to use classic dialogs.

The error is Sys.InvalidOperationException: Sys.InvalidOperationException: Component 'RadEditor1_dialogOpener' was not found.

When not enabled RadEditor should merely show its content, when Enabled is toggled to true it should render toolbars and add its functionality.

A possible workaround is using the Visible property instead and a div with runat=server as a placeholder for the editor while it is not rendered (its Content property will still return the HTML in it). Thus, the innerHTML server property of the div can be used to set the HTML from RadEditor in it.

 If there are textarea tags or style tags in the HTML content of RadEditor, after completing the spell check  the content is repeated several times. 

When HTML content is set to the editor and has stylization with the inline style attribute the 'ConvertInlineStylesToAttributes' filter converts some of them to attributes, but after a post back they disappear.

When RadEditor's ContentAreaMode is Div the entire page is printed instead of just the content. 

Possible solution is changing the mode to Iframe as it is by default. 

Currently, RadEditor supports single level context menu only. We had one of the requirement to have a multilevel context menu (like - menu --> sub menu). It would be really nice to have this feature in the upcoming release as it makes the RadEditor more user friendly.

-- Rahul.