Q1 2013 (Version number: 2013.1.220)

Important changes:

RadButton
What is changed: RadButton's rendering so it is HTML5 compliant. The change is described in this forum thread.

RadEditor
What is changed: Raises domChange event for every newly created link in InsertLinkCommand. The change is described in this forum thread.

RadGrid
What is changed: Properties for invisible columns are not persisted in ViewState. The change is described in this forum thread.

RadImageEditor
What is changed: RadImageEditor New Tools sprites are placed in Skins common folder. Until the change we were using different sprite for each skin, which is too resource consuming. Currently there are only two sprites for the tools - Dark or Light Sprite, which are used depending on the skin.

RadWindow

Misplaced titlebar after autosizing when in RTL mode and RenderMode=Classic—fixed as of R2 2017 SP1.

Q2 2013 (Version number: 2013.2.611)

Important changes:

RadAsyncUpload
Improved: In order to upload files bigger than 2GB the type of the ContentLength properties in the AsyncUpload is changed to Int64.

RadComboBox
Changed: Image element is rendered after the checkbox element. The change is made in order to be consistent with the rest of controls.

RadEditor
Changed: The Track Changes dialog of RadEditor is now obsolete. Use the EnableTrackChanges property to enable an improved track changes functionality that offers better interaction and usability.
Improved: The insert list command in RadEditor.
Improved: The Align command in RadEditor to be consistent x-browser.
Improved: Indent/Outdent command in RadEditor. Now uses CSS styling instead of <blockquote> tags to indent block content

These commands use pure DOM manipulations and do not rely on the underlying browser commands. The behavior thus is consistent across browsers and differs from the way these commands have been working thus far.
Please, keep in mind that these commands manipulate block nodes and lines separated by <br/> tags are still within a common block container, therefore lines separated by line breaks will be handles together by the InsertList, Align, Indent and Outdent commands.

RadGrid
Changed: When grouping a RadGrid field with Aggregate set to Count the DataType of the aggregate column is changed from decimal to int.

RadFormDecorator
Changed: The text inputs decorated with RadFormDecorator now have fixed height for consistency with RadInput.

RadHtmlChart
Changed: The Items property for manipulating series items of the RadHtmlChart is obsolete and it is replaced by the SeriesItems property. SeriesItems is the improved and fine-grained approach to managing series items in the RadHtmlChart.
Changed: The background of the tooltip is now determined by the series item's color. The change is made for better consistency with the appearance setup of the series item.

Q2 2013 SP1 (Version number: 2013.2.717)

Important changes:

RadWindow
Changed: The RadWindow Light Rendering Toolbar buttons are now rendered with input element of type button, instead of a button element. The change is made to avoid closing the RadWindow when pressing enter with a focused TextBox in the ContentTemplate of the control.

Q3 2013 (Version number: 2013.3.1015)

Important changes:

RadEditor
The inline commands of RadEditor (bold, italic, underline, strikethrough) are now DOM based, instead of using browser behavior, which previously resulted in the concrete browser instance defining the wrapping tag of the command.

MozEmStrongFilter is removed from the default Filters collection of RadEditor as it was interfering with the DOM based inline commands.

• You can configure the Telerik controls to use one of the newer skins that we introduced recently, instead of the obsolete ones.
• You can modify one of the existing skins in order to create a new one that will have the name and appearance of your choosing. The Visual Style Builder will be quite useful for this purpose.

• http://demos.telerik.com/aspnet-ajax/combobox/examples/loadondemand/odata/defaultcs.aspx
• http://demos.telerik.com/aspnet-ajax/listbox/examples/loadondemand/odata/defaultcs.aspx
• http://demos.telerik.com/aspnet-ajax/menu/examples/loadondemand/odata/defaultcs.aspx
• http://demos.telerik.com/aspnet-ajax/treeview/examples/loadondemand/odata/defaultcs.aspx

Q3 2014 (Version number: 2014.3.1024)

RadDiagram

Replaced DataBackgroundField property in BindingSettings.ShapeSettings with DataFillColorField.
Replaced ShapeDefaultsSettings.Background with ShapeDefaultsSettings.FillSettings.Color.
Replaced DataHoverBackgroundField property in BindingSettings.ShapeSettings with DataHoverFillColorField.
Replaced HoverSettings.Background property in a DiagramShape with HoverSettings.FillSettings.Color.
Replaced Rotatable and Resizable properties of the Diagram and in the ShapeDefaultsSettings composite property with EditableSettings.Rotate and EditableSettings.Resize.
Replaced Background property of a DiagramShape with a fine-grained FillSettings composite property.
DiagramConnectionPoint class is now used instead of ConnectionPoint class.
ZoomRate property of the Diagram now defines the zoom step instead of the zoom scale altogether. The default value of this property is changed from 1.1 to 0.1.

RadEditor

Due to legacy code refactoring the RadEditorCommandList global object is now obsolete. Use Telerik.Web.UI.Editor.CommandList full name instead, as explained in this documentation article.

RadHtmlChart

The OnClientSeriesClicked and OnClientSeriesHovered events of RadHtmlChart are now obsolete. Use the OnSeriesClick and OnSeriesHover events in the ClientEvents composite property instead, as shown in the following help article: http://www.telerik.com/help/aspnet-ajax/htmlchart-client-side-events.html

Changed: The div element which wraps chart's tooltips is not rendered inside the chart anymore but as the bottom element of the body. If the chart is placed inside a pop-up element (e.g. RadWindow, RadNotification, etc) with a higher z-index tooltips will be hidden behind it. You must ensure a higher z-index for the tooltips, as illustrated in the Common Issues help article, in the section called "Тooltips are Hidden Behind RadWindow and/or RadNotification".

RadGrid

The Columns collection of the Export Infrastructure is not populated by columns that do not have HeaderStyle.Width set. This can cause issues with formatting an Excel export file if you loop through the e.ExportStructure.Tables(0).Columns collection - it may return 0 or a number smaller than the number of columns.

Q1 2015 (Version number: 2015.1.225)

RadCalendar

• SpecialDays cannot be deselected visually when they have CssClass defined
  

RadDock
The command buttons of RadDock are span elements instead of button elements when RenderMode="Lightweight".

RadEditor

• Remove the Iframe which holds the textarea element in HTML mode.
• Strip content functionality now uses DOM operations.
• Modifying inline commands to handle formatted block elements.

• Ability to set the RadFileExplorer paths (ViewPaths, UploadPaths, EditPaths) before PagePreRender and after PageLoad.
• RadAsyncUpload is the default upload tool.

Q3 2015 SP1 (Version number: 2015.3.1111)

Common

There is a issue, causing wrong order of script registrations in the header on the page. Possible impacts:

1. JS erros on the page, such as:  $ is not defined.
2. Inability to load styles on the page.

The issue is already fixed as from our 2015.3.1124 internal build. Fixed as of Q1 2016.

RadButton

RadButton with RenderMode=Lightweight will not raise its OnClick event if it performs an AJAX request and the text is clicked under Chrome and Edge. This will be fixed in the Q1 2016 release and the fix will be available in the 2015.3.1124 internal build. You can find more details in the following sticky thread: The server-side OnClick event is not raised when clicking on the Button text (Lightweight RenderMode, Chrome/Edge browsers, Q3 2015 SP1 release).

TileList

There are some issues with the events under mobile devices when Lightweight RenderMode is used. Thus, navigation requires a double tap and there are problems with taps and dragging. These will be fixed in Q1 2016 and in all internal builds after  the 25^th of November 2015.

Q1 2016 (Version number: 2016.1.113)

RadButton

• The CommandName and CommandArgument of RadButton are not available in the ClientClicking eventargs
  
  This bug is fixed in Q1 2016 SP1.
  
  Possible workaround is to use the sender parameter to obtain the CommandName and CommandArgument:
  <script type="text/javascript">

      function btnEdit_Clicking(sender, eventArgs) {

          alert(sender.get_commandName());

          alert(sender.get_commandArgument());

      }

  </script>

   

  <telerik:RadButton ID="RadButton2" AutoPostBack="false" runat="server" Text="Click Me" OnClientClicking="btnEdit_Clicking" CommandArgument="Name"></telerik:RadButton>
  
  
  
• AccessKey doesn't work in IE11 using Lightweight rendering
  
  This bug is fixed in Q1 2016 SP1.

RadSplitter

• The client docking events of RazSlidingZone are not triggered properly
  
  This bug is fixed in Q1 2016 SP1.
  
  The client events of RazSlidingZone are not triggered properly when the zone is placed in a nested Splitter.
  
  
  
• Sliding zone tabs text is upside down in Firefox
  
  This bug is fixed in Q1 2016 SP1.
  
  You can download an example with a workouround from the linked item or via this download link—http://feedback.telerik.com/AttachmentDownload/24565.

RadTileList

• TileList OnTileClick handler does not work in data binding scenario
  
  This bug is fixed in Q1 2016 SP1.

Q1 2016 SP1 (Version number: 2016.1.225)

Common

• Important change: In the Lightweight Render Mode all UI for ASP.NET AJAX controls do not have a default font any more. This means the controls do not have font-size, font-family, font-weight and font-style predefined and inherit the font-size of the <body> element if such is set. Otherwise, the default browser values apply. This provides all Telerik controls on the page with the same look and feel by making use of their elastic design capabilities. You can find additional details in the following resources:

  • Fonts
  • Visual and Dimension Improvements in UI for ASP.NET AJAX

• RadWindow with AutoSize=true is not positioned properly. Fixed as of R2 2016.
  
  Fix: Use OnClientAutoSizeEnd event and call the center() method to position RadWindow properly. 

  <script>

      function OnClientAutoSizeEnd(sender, args) {

          sender.center();

      }

  </script>

   

  <telerik:RadWindow ID="RadWindow1" runat="server" OpenerElementID="Button1"

      AutoSize="true" Modal="true" OnClientAutoSizeEnd="OnClientAutoSizeEnd">

      <ContentTemplate>

          <div style="width: 600px; height: 400px; background: yellow;">

              dummy content for autosizing

          </div>

      </ContentTemplate>

  </telerik:RadWindow>

   

  <asp:Button ID="Button1" Text="open RW" runat="server" />

   

• Lightweight RadWindow with RestrictionZoneID and overflow hidden parent jumps on dragging under FireFox. Fixed as of R2 2016.
  
  Symptom: When dragged, RadWindow jumps to most top-left position possible. Instead of being dragged to the position where mouse is pointed to.
  
  

• JavaScript error on opening a Classic RadWindow with enabled AutoSize and AutoSizeBehaviors Height/HeightProportional. Fixed as of R2 2016.
  
  Symptom: No content is being loaded into RadWindow when shown.

RadImageEditor

• It is not possible to draw in IE and Edge on mobile devices in RadImageEditor. Fixed as of R2 2016.
  
  Symptom: In a mobile device, drawing on the canvas of ImageEditor does not lead to any changes on the image to be edited. 
  
  Fix: Hard-coding touch-action:none CSS property as inline style. 

  <telerik:RadImageEditor ID="RadImageEditor" runat="server" style="touch-action:none;"></telerik:RadImageEditor>

RadMenu

• Styling changes in Metro and MetroTouch skins in Lightweight RenderMode for RadMenu, introduced with Q1 2016.1.225 SP1 release
  
  Symptom: The styling of the Metro and MetroTouch Lightweight skins of the RadMenu has changed.
  
  Fix: Use the suggested in the article CSS rules to revert back to the look of the skins before the Q1 2016 SP1 release.

RadPanelBar

• Styling changes in MetroTouch skin in Lightweight RenderMode for RadPanelbar, introduced with Q1 2016.1.225 SP1 release
  
  Symptom: The styling of the MetroTouch Lightweight skin of the RadPanelBar has changed. 
  
  Fix: Use the suggested in the article CSS rules to revert back to the look of the skin before the Q1 2016 SP1 release.

• The DialogsCssFile property breaks the appearance of a custom skin - When setting the DialogsCssFile property, the generated markup of the RadEditor wrapper changes from 
  
  Radeditor RadEditor_<MyCustomSkin> reWrapper to Radeditor <MyCustomSkin> reWrapper, which prevents the custom skins to get applied to RadEditor. 
  
  To fix the problem explicitly set the RenderMode property of RadEditor to "Lightweight", i.e.
  
  
  <telerik:RadEditor RenderMode="Lightweight" DialogsCssFile="~/MyCustomSkin/DialogContents.css" ID="RadEditor1" runat="server" Skin="MyCustomSkin" EnableEmbeddedSkins="false">

              <ImageManager ViewPaths="~/" UploadPaths="~/" />

  </telerik:RadEditor>
  
  
  
  
• Using ToolsFile property from the markup disregards Lightweight rendering configured from the web.config. 
  
  Logged item: http://feedback.telerik.com/Project/108/Feedback/Details/191004. Fixed as of R2 2016 SP1.
  
  Description: When you enable Lightweight rendering from the web.config and having a RadEditor control with ToolsFile in the markup, Classic mode will resolved and rendered.  
  
  Workarounds: You cna setup the ToolsFile.xml in the code behind:
  RadEditor1.ToolsFile = "~/ToolsFile.xml";

RadWindow

• Calling set_modal(true) on a modal RadWindow makes it non-modal.
  
  Simple example of the problem:
  
  
  <telerik:RadWindowManager ID="RadWindowManager1" runat="server" Modal="true"></telerik:RadWindowManager>

  <asp:Button ID="Button1" Text="test" OnClientClick="test(); return false;" runat="server" />

  <script>

      function test() {

          var wnd = radopen();

          wnd.set_modal(true);

      }

  </script>
  A workaround is to add a check first:
  
  if (!wnd.get_modal()) {

      wnd.set_modal(true);

  }
  
  This issue is fixed in R2 2016 SP1.

R2 2016 SP1 (Version number: 2016.2.607)

RadEditor

• You cannot add tools (via markup or via server code) when a ToolsFile is used. Regression since R2 2016 (2016.2.504). Fixed in R3 2016.

R3 2016 (Version number: 2016.3.914)

• Double checkbox and radio button icons under Chrome, Safari and Edge with certain DecoratedControls combinations under Classic Render Mode. The easiest workaround is to use the Lightweight RenderMode. This issue will be fixed in R3 2016 SP1.

R3 2016 SP1 (Version number: 2016.3.1018)

RadEditor

• Uncaught TypeError: this._contextMenuFunctionality.dispose is not a function (Chrome) or Object doesn't support property or method 'dispose' (IE) error is thrown when a RadEditor with RenderMode=Classic is disposed on a page that uses RadScriptManager with EnableScriptCombine=true. There are three workarounds provided in the article above and in the attachment to this post. Fixed in R3 2016 SP2 (2016.3.1027).

RadFileExplorer

• The toolbar delete button is enabled only if the selected item's parent folder can be deleted. A workaround is provided in the item. Fixed as of R1 2017.

R1 2017 (Version number: 2017.1.118)

RadButton, RadFormDecorator

• Broken WebResource request caused by a missing image (radFormSprite.png). Fixed as of R2 2017.
• Whitespace or broken font icon on radio buttons when RenderMode=Classic and a RadControl with RenderMode=Lightweight is on the page. Fixed as of R3 2017 SP1, does not exist in R2 2017.

RadComboBox

• Missing indication for loaded items in RadComboBox MoreResultsBox. Fixed as of R2 2017.

RadGrid

• OnCommand is not fired when ConfirmDialogType="RadWindow". Fixed as of R1 2017 SP1.

RadNotification

• The close icon is missing in Classic render mode with Skin=Bootstrap. Fixed as of R2 2017 SP1.

RadProgressBar

• Skins are not downloaded, a 404 request is sent for the SASS file (fixed as of R2 2017).

RadSplitter

• Missing skin colors in sliding panes as of R1 2017 (fixed as of R2 2017).

RadTileList

• Missing colors and background colors for many skins (fixed as of R2 2017).

RadToolTip

• Missing colors and backgrounds in some skins (fixed as of R2 2017): .
• Whitespace between callout and body in Classic RenderMode. Workaround for Bottom positions:
  
  
  div.rtShadow.RadToolTip_Metro div.rtCalloutTopLeft,

  div.rtShadow.RadToolTip_Metro div.rtCalloutTopRight

  {

      margin-top: -7px;

  }

RadWindow

• Wrong colors for some skins (Classic RenderMode is fixed as of R2 2017,  Metro colors for the Lightweight mode are fixed as of R2 2017 SP1).
• Wrong order of buttons in RTL mode in Lightweight RenderMode (fixed as of R2 2017).
• Command buttons (e.g., Close) appear to not work after maximizing a RadWindow that does not have the Maximize or Resize behavior enabled. Happens due to a JS error. Fixed as of R1 2017 SP1.
• RadAlert/RadConfirm in mode: removing the icon, or setting a custom one, keeps showing the default icon (fixed as of R2 2017).

R1 2017 SP1 (Version number: 2017.1.228)

RadButton

• Checked checkboxes have misplaced backgrounds (fixed as of R2 2017).
• Distorted appearance in Classic RenderMode.

RadMenu

• The selected menu item is gray instead of yellow when RadMenu has a Glow skin in Classic render mode (fixed as of R2 2017 SP1)
• When a control inside a Template is focused, the focus of the nested control is immediately lost  (fixed as of R2 2017).

RadSplitter, RadFileExplorer and RadEditor dialogs

• Gray background in RadSplitter, RadFileExplorer and RadEditor dialogs with RenderMode Classic and Default/Silk/Bootstrap . 

RadWindow

• Controls like RadTreeView, RadTabStrip and other UL elements in RadWindow float to the right under Firefox 52 and Chrome 58, because the browsers started reading a CSS rule differently. Fixed as of R2 2017.

R2 2017 (Version number: 2017.2.503)

Common

• Office2010Black has white backgrounds on some controls, instead of the previous light-gray.

RadFormDecorator

• RenderMode="Classic" with Silk skin renders the backgrounds of the decorated textboxes/ elements in gray (fixed as of R2 2017 SP1)

RadTabStrip

• The disabled tabs do nоt look disabled in Classic render mode

RadWindow

• Wrong width of the RadAlert/ConfirmPrompt buttons wrapper in Material Skin (fixed as of R2 2017 SP1)

R2 2017 SP2 (Version number: 2017.2.711)

RadAsyncUpload

R1 2018 (Version number: 2018.1.117)

Common

The Telerik.Web.Design.dll assembly is no longer added to the GAC by the automated installer and this can cause design-time errors if you upgrade via the Upgrade Wizard and your project did not have an explicit reference to the Telerik.Web.Design.dll file in the project folder. You can read more in this section of the documentation: Error Creating Control Failed To Create Designer after upgrade to R1 2018.

*** Updated on March 7, 2018 ***

The issue is already fixed in version 2018.1.215.2 of Telerik ASP.NET AJAX VSExtensions 
From the Release notes -> Telerik.Web.Design.dll is not added to the Bin folder of a newly created Telerik AJAX site/app. 

To fix the problem:

• Download the latest Telerik ASP.NET AJAX VSExtensions installation from the VS Marketplace, install it and restart your Visual Studio.
• or Wait for the next official R2 2018 release of Telerik UI for ASP.NET AJAX, to be out in May.
• or Place manually the Telerik.Web.Design.dll in the Bin folder of the app
  
   

RadFileExplorer

You may be unable to rename files or to drag-and-drop files to the treeview to move them. Both of these features internally go through the Rename feature and its security was improved for R1 2018. If rename or move does not work for you, there are several likely reasons:

• The user does not have permissions to write to that folder. To allow the operation, the current folder must be present in the DeletePaths and UploadPaths.
• The file extension that is entered is not present in the SearchPatterns, which means that the user should not be able to tamper with such files.
• Some custom content providers that use some form of IDs instead of physical paths may be unable to move or rename files even when permissions are in order. This will be fixed in R2 2018. Note that the custom provider must implement all necessary methods, including GetFileName(path).

All known regression issues in this release are fixed in R2 2018 SP1.

Common

The jQuery version that is embedded in the Telerik.Web.UI.dll assembly is upgraded to 3.3.1.
This is done to improve stability, compatibility with modern browsers and security, as well as optimize by dropping support for browsers like IE7 and IE8 that the UI for ASP.NET AJAX suite has not been supporting for years. This upgrade will allow the controls to stay up to date with modern web development and current standards.

This change applies to the window.$telerik.$ variable and to the global jQuery references only if you manually populate them through code similar to window.$ = $telerik.$; or if you have the following script reference <asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQueryInclude.js" />
You may find useful the migration guide provided by jQuery: https://jquery.com/upgrade-guide/3.0/.

If you want to use a different version of jQuery (including downgrade to version 1.11.1), follow the Disabling the Embedded jQuery article.

If you get errors like access to strict mode caller function is censored especially under Firefox, the solution is to downgrade to jQuery 1.11.1 that the suite used before. Below is some sample markup.

How to disable the built-in jQuery 3.3.1 and use 1.11.1:

Here follows a list of the known issues caused by jQuery3

RadAjaxPanel

jQuery button click in RadAjaxPanel under FireFox causes TypeError: access to strict mode caller function is censored. This is caused by the 'use strict' that jQuery 3 begins with. Fixed in R2 2018 SP1.

RadAutoCompleteBox

Dropdown extends to the left and screen boundary detection to the left does not work in R2 2018. This is caused by the 'use strict' that jQuery 3 begins with. Fixed in R2 2018 SP1.

RadDropDownList

Cannot postback under Firefox, TypeError: access to strict mode caller function is censored is thrown. This is caused by the 'use strict' that jQuery 3 begins with. Fixed in R2 2018 SP1.

RadFileExplorer

Cannot rename files under Firefox, TypeError: access to strict mode caller function is censored is thrown. This is caused by the 'use strict' that jQuery 3 begins with. Fixed in R2 2018 SP1.

Cannot upload files under Firefox, TypeError: access to strict mode caller function is censored is thrown. This is caused by the 'use strict' that jQuery 3 begins with. Fixed in R2 2018 SP1.

RadListBox

Server events are not raised under Firefox (selection, reorder, transfer, drag-and-drop, etc.), TypeError: access to strict mode caller function is censored is thrown. This is caused by the 'use strict' that jQuery 3 begins with. Fixed in R2 2018 SP1.

RadSearchBox

Cannot fire OnSearch under Firefox, TypeError: access to strict mode caller function is censored is thrown. This is caused by the 'use strict' that jQuery 3 begins with. Fixed in R2 2018 SP1.

RadWizard

Cannot change step with a postback under Firefox , TypeError: access to strict mode caller function is censored is thrown. This is caused by the 'use strict' that jQuery 3 begins with. Fixed in R2 2018 SP1.

Other known issues in this release

TypeScript Definitions

The .ts definitions file is wrong in the initial release and does not contain the actual definitions. You can find the file at the bottom of this post. Fixed in R2 2018 SP1.

R2 2018 SP1 (Version number: 2018.2.710)

Common

The embedded jQuery is replaced with 1.12.4
This was necessary because of incompatibilities jQuery 3.3.1 has with the MS AJAX framework and its __doPostBack() method - see the post above for more details.

RadHtmlChart

• The Step and Skip properties were removed from series labels because they only apply to axis labels and they are confusing when in the series labels. This means that the following will fail to compile:

  <telerik:RadHtmlChart runat="server" ID="RadHtmlChart1">

      <PlotArea>

          <Series>

              <telerik:AreaSeries>

                  <LabelsAppearance Skip="1" Step="2"></LabelsAppearance>

              </telerik:AreaSeries>

          </Series>

      </PlotArea>

  </telerik:RadHtmlChart>

   

• Improvements were made on the escaping of symbols and you should review the following two articles. If you have not followed the guidance in them, special symbols in field names or improperly escaped new line symbols may cause a change in the behavior you have:
  • RadHtmlChart Cannot be Bound to a Data Source that Has Special Characters in Its Field Names
  • Multiline Labels (see the end of the article)

• Custom marker class is changed from .k-marker-<marker.shape> to .k-i-marker-<marker.shape>

• Backported jQuery XSS issue security fix. The version remains the same - 1.12.4. This change means that XHR requests for scripts through the $telerik.$.ajax() will no longer execute those scripts unless dataType: "script" is set in the options, which is the security fix that jQuery implemented and is correct behavior. This is necessary because this issue was reported as fixed in 1.12.0 and so we upgraded to the latest (1.12.4) to get this fix. It turns out, however, that the jQuery team silently reverted it in 1.12.3 without posting in the 1.12.3 release notes. To minimize changes, we used their guidance to backport the fix. Important: static security scans will still report the jQuery brought by Telerik UI for ASP.NET AJAX as being vulnerable, and this is going to be a false positive as of R1 2019. The jQuery version brought by Telerik UI for ASP.NET AJAX cannot be upgraded to 3.x, because this breaks the MS AJAX framework (we attempted this in R2 2018).

• When uploading a large file and the ChunkSize property is set the excel files are partially uploaded - the problem was fixed in the LIB (nightly build) 2019.1.308 and will not exist in R2 2019.
  
  You can download the LIB from https://www.telerik.com/account/product-download?product=RCAJAX -> click on the Internal Builds tab -> download Telerik_UI_for_ASP.NET_AJAX_2019_1_308_Dev_hotfix.zip or Telerik_UI_for_ASP.NET_AJAX_2019_1_308_Trial_hotfix.zip depending on your license.

• Exporting to Xlsx or Biff throws an Exception: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index. This happens when the last column in the columns collection has either the Visible, Display or Exportable property set to false. The Issue is logged at After upgrading to 2019.1.115 Export to XLSX throws an exception: Index was out of range with critical priority.
  
  
  
• HeaderContextMenu goes out of screen boundaries. See the ContextMenu section below for more information.
  
  
  

• Menu goes out of screen boundaries after the opening animation finished. The first time the issue was observed is when it is used inside RadGrid as HeaderContextMenu, but the same applies for standalone ContextMenu control. Bug was logged in the Feedback Portal at as RadGrid HeaderContextMenu out of screen boundary but the workaround posted in it actually applies for the ContextMenu.
  
  

• When the ToolProviderID property is set, the page errors out with "R.get_canAcceptTrackChange is not a function" - the problem will be fixed in the upcoming R1 2019 SP1 due in February. You can find a workaround in the following feedback portal bug item: R.get_canAcceptTrackChange is not a function error when using ToolProviderID.
  
  

R3 2019 (Version number: 2019.3.916)

RadDatePicker and RadDateTimePicker

• JavaScript error: Uncaught TypeError: Cannot read property '_popupButton' of null JS error when clicking OK or Cancel in the the month/year dialog. You can find more details here.
  
  The problem is fixed in R3 2019 SP1 (version 2019.3.1023).
  
  
  

R1 2020 (Version number: 2020.1.114)

RadAsyncUpload

• AllowedCustomMetaDataTypes=Telerik.Web.UI.AsyncUploadConfiguration is enabled by default to improve the application security and allows the built-in Telerik type only. You can find more information here.

• The RadHtmlChart appearance properties are not fully applied in R1 2020 (e.g. XAxis.MajorGridlines="false", ChartTitle.Appearance.TextStyle.Font, etc.). You can find more details here.
  
  The problem is scheduled for R1 2020 SP1

RadFileExplorer

• Value property is not supported by RadToolBarDropDown error in R1 2020 when adding a dropdown to FileExplorer toolbar. Feedback portal item here.
  
  Scheduled for R2 2020 SP1

Visual Studio Extensions for Telerik® UI for ASP.NET AJAX (VSX)

• [Update] The problem is fixed in version 2020.1.122 of Visual Studio Extensions for Telerik® UI for ASP.NET AJAX which you can obtain from the VS marketplace: 
  
  [/Update]
  
  If your app is configured to use the Classic RenderMode of the Telerik AJAX components, you may experience appearance problems (like displacements, different metrics, fonts, and colors) after upgrading to R1 2020 due to that the Telerik VSX extensions for ASP.NET AJAX tool puts
  
  <add key="Telerik.Web.UI.RenderMode" value="lightweight" />
  
  in the appSettings section of the web.config file. This setting forces the Telerik AJAX components to use their Lightweight render mode (the Default rendering is the Classic).
  
  To solve the issue remove the <add key="Telerik.Web.UI.RenderMode" value="lightweight" /> line from the web.config or upgrade to the latest version of the Telerik AJAX VSX extension. You will also not experience the issue if you perform a Manual Upgrade.

R3 2020 SP1 (Version number: 2020.3.1021)

RadClientExportManager:

• Export to PDF throws JS error when no jQuery is loaded in window.$. There are two workarounds for it
  1. set jQuery globally with a script:
     

     window.$ = window.$ || $telerik.$;

     
     
  2. Include a script reference to the Telerik.Web.UI.Common.jQueryInclude.js: https://docs.telerik.com/devtools/aspnet-ajax/general-information/using-jquery/using-jquery#using-the-jquery-brought-by-telerik 

     1.   <telerik:RadScriptManager ID="RadScriptManager1" runat="server">
                    <Scripts>
                        <asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.Core.js" />
                        <asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQuery.js" />
                        <asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQueryInclude.js" />
                    </Scripts>
                </telerik:RadScriptManager>

Regards,
Peter Milchev
Progress Telerik

R1 2021 SP1 (Version number 2021.1.224)

RadGantt:

• OnTaskUpdate server event is not triggered when editing in TreeList part

RadSpreadsheet:

• Uncaught TypeError: Cannot read property 'offsetWidth' of undefined when updating a cell in spreadsheet 

RadTimeline:

• The timeline date item is misaligned with the track in horizontal mode