Release History

Telerik UI for ASP.NET AJAX 2026.1.421

April 22, 2026

Security

FIXED

• Addressed CVE-2026-6022
• Addressed CVE-2026-6023

Common

NEW

• Telerik Licensing minimal required version is updated to 1.8.2.
• Telerik Document Processing Library (DPL) version is updated to 2026.1.402.

AsyncUpload

Breaking Changes

• CSRF validation is now enabled by default for all upload requests. Applications that do not use ASP.NET Session State must add to appSettings. Applications using WebResourceSession handler are not affected. For more information, see CSRF Protection.
• The legacy and already obsolete IFrame, Silverlight and Flash upload modules have been removed. RadAsyncUpload now exclusively uses the File API module.
• The DisablePlugins property has been removed. Remove any references to it from your markup or code-behind.
• The get_loadedModuleName() client-side method has been removed. Remove any calls to it from your client-side code.
• The FileFilters property is no longer functional as it relied on the removed Flash and Silverlight modules. Use the HTML5 accept attribute on the file input instead.
• The Telerik.Web.UI.RadAsyncUpload.Modules.Flash and Telerik.Web.UI.RadAsyncUpload.Modules.Silverlight client-side objects no longer exist. Remove any JavaScript workarounds referencing them.

ClientDataSource

NEW

• Added OData v4 transport option.

Filter

FIXED

• Replaced Newtonsoft.Json dependency with a built-in serializer for filter expression serialization.

DataPager

FIXED

• Fixed 'field' keyword conflict in RadDataPagerDesigner property accessor causing design-time errors.

Editor

NEW

• MediaManager now outputs HTML5 video and audio elements for browser-supported formats (mp4, webm, ogv, mp3, wav, ogg, oga) instead of the obsolete object/embed tags. Legacy formats (e.g. avi, wmv) still use embed. The WMP Properties tab has been replaced with HTML5 attributes (controls, autoplay, loop, muted, preload) for supported formats.
• Improved keyboard navigation and screen reader support in RadEditor toolbar dropdowns (FontName, FontSize, RealFontSize, ForeColor, BackColor, InsertSymbol, InsertTable etc.).

FIXED

• Design rendering failure with Uncaught TypeError: Cannot read properties of null (reading 'commonAncestorContainer') when using ToolbarMode="RibbonBarShowOnFocus"
• Keyboard selection not working in toolbar dropdowns (FontName, FontSize, RealFontSize).
• Missing ARIA attributes on the HTML mode textarea when EnableAriaSupport is enabled.
• Cell Properties - Preview only shows top-left cell styling when applying changes to multiple top-row cells

Grid

FIXED

• Fixed HeaderContext filter menu throwing '_linkElement' undefined error after expand animation ends.

NumericTextBox

NEW

• Added EnableMobilePattern property for triggering the numeric keyboard on mobile devices.

PdfProcessing

NEW

• Optimized the export of Functions.
• Improved font handling during document import.
• Introduced API for Cloning RadFixedPages and for splitting RadFixedDocument into pages.
• Implement AutoTag Tables from document Primitives.
• Introduced support for PDF Portfolios.
• Implemented Exponential Interpolation Function.

FIXED

• The import performance is reduced when having XObject instances with many Shading elements.
• PdfStreamWriter: Merging PDF documents causes blank pages.
• An InvalidCastException when importing a document.
• A NullReferenceException is thrown when importing a document with EmbeddedFile without Subtype.

SpeechToTextButton

FIXED

• Fixed SpeechToTextButton Designer throwing an error at design time.

SpreadProcessing

NEW

• XlsFormatProvider: Add support for hidden rows.
• Add support for Superscript/Subscript formatting option.
• Introduced support for notes in XLS format.
• Add support for Strikethrough formatting option.
• Introduced support for images when importing and exporting XLS documents.

FIXED

• SpreadProcessing: XLSX image lock aspect ratio imports incorrectly when importing a document with PictureLockingElement which noChangeAspect attribute is boolean
• XlsFormatProvider: InvalidOperationException is thrown when importing a document with an unsupported BIFF record.
• Importing file with comments part with other name than comments.xml throws and exception.

Window

FIXED

• RadWindow predefined dialogs do not fully expose required accessibility attributes.

WordsProcessing

FIXED

• PdfFormatProvider: Justified text alignment is not respected for specific text content.