RadAsyncUpload does not upload files in iOS 8 Safari. After selecting a file/files for upload, their upload remains as pending and never reaches the end of the process.
Note: there is a known iOS 8 Safari issue with <input type="file" />

Workaround: 

function encodeRowContent() {
    var asyncUpload = $find('<%= RadAsync_FileUpload.ClientID%>');
    var $ = $telerik.$;
    asyncUpload._updateRowContent = function (row, inputValue) {
        var $progress,
            $content = $("<span class='ruUploadProgress'>" + $telerik.htmlEncode(this._getFileName(inputValue)) + "</span>");

        $(row).removeClass("ruSelectWrap")
                .addClass("ruFileLI ruUploading")
                .prepend("<span class='radIcon'></span>");

        if (this._isManualUpload())
            $content.addClass("ruUploadOnHold");

        if (this._enableInlineProgress) {
            $progress = $('<span class="ruFileProgressWrap"><span class="ruFileProgress"></span></span>');
            $content.append($progress);
        }

        $('.ruFakeInput, .ruBrowse', row).remove();
        $(".ruFileWrap", row).append($content); // Replace fake input
    }
}

Sys.Application.add_load(encodeRowContent);

RadAsyncUpload "Drop Files here" element remains visible when dragging a file quickly over and out of the DragZone

Replicable in File Upload with Drag and Drop live demo.

Drag a file quickly through the DragZone without dropping it. The "Drop Files Here" element is shown but doesn't get hidden when the mouse leaves the DragZone (ondragleave).

Here's the scenario: 
User changes the extension of a .js file to .jpg and upload the file, by no means we are able to restrict the user from uploading the file. 
Is there a way to stop user from uploading based on associated mimetype ?

The MaxFileSize property is an int - this means a limit over 2GB can't be set. Please change this property to a long. 

Workaround:
Set DisablePlugins="true" or
set RenderMode="Lightweight"

Documentation says Firefox should be ok with LastModifiedDate, but it's not.  It's consistently being set to 1/1/0001 12:00:00 AM, which is not useful.

Happens in any RadAsyncUpload example if you look at the value for LastModifiedDate in the AsyncUploadedFile objects.

Works fine in Chrome, Edge.  Fails in Firefox for Mac or Windows.

This issue is observed only in R1 2020. The solution is to not disable the FileAPI.

Reproduction steps:

<script>
    Telerik.Web.UI.RadAsyncUpload.Modules.FileApi.isAvailable = function () { return false; };
    Telerik.Web.UI.RadAsyncUpload.Modules.Flash.isAvailable = function () { return false; };
    Telerik.Web.UI.RadAsyncUpload.Modules.Silverlight.isAvailable = function () { return false; };
</script>
<telerik:RadAsyncUpload runat="server" ID="RadAsyncUpload1" ></telerik:RadAsyncUpload>

Recently, Chrome version has been updated our all the user’s system as 117.xxx.xxx.

After updating the Chrome version and RadAsyncUpload is not working and getting the below error message. So, user unable to perform any upload action on this.

This is control using in production live application and it affecting our day-to day business.

Please provide your solution as soon as possible.

Error – Message :

Uncaught Error while uploading, <div></div><pre>{"fileInfo":{"FileName":"README.md","ContentType":null,"ContentLength":5798,"DateJson":null,"Index":0}, "metaData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}</pre>

Telerik version - 2011.1.614.35
RadAsyncUpload issues on Safari 5.1.7, IE 9 and Chrome 28.0.1500.95 -

Following is the list of issues seen on the mentioned browsers -
a.  On Safari, the upload file functionality doesn't work at all –
On Safari, when a file is selected from the Open dialog box, the dialog box closes and nothing happens after that. The file is not shown in the upload control, and no event is fired.

b.  On IE, the Open dialog box shows the specific file types by default, whereas on Chrome, all file types are shown by default –
We have set the ‘AllowedFileExtensions’ property of the RadAsyncUpload to “image/png,image/x-png,image/jpeg,image/pjpeg,image/gif,.x-png,.gif,.jpeg,.jpg,.png”. On IE 9, when the Open dialog box is opened, by default, the mentioned extensions as selected in the File Type drop down. Whereas, on Chrome, ‘All’ is shown in the File Type drop down. We would like this behavior to be consistent. Is it possible to show ‘All’ on IE9?

c.  On Chrome, uploading a file with size greater than the mentioned file size gives a Silverlight error (Refer SilverlightPluginError.png) –
i.	The MaxFileSize is set to 500 KB. When user tries to upload a file with size greater than 500 KB, the gets an alert message indicating he cannot upload a file beyond the said size. This works fine on all browsers other than Chrome. On Chrome, when a file with size greater than 500 KB is selected from the Open dialog box, the page seems to hang for some time. Then an alert message is displayed with following message –
The following plug-in is unresponsive: Unknown
Would you like to stop it?
ii.	Upon clicking ‘Yes’, following message is shown below the Chrome address bar 
Silverlight plug-in has crashed
iii.	And, the alert indicating file size greater than 500 KB cannot be uploaded is shown.

when deleting files from radasyncupload via the "built-in" delete button, "get_fileName()" method in both the upload_removing and upload_removed events returns correct data. However, when deleting files via the api, the get_fileName() method returns bad content.

built-in button something like:
document.pdf

api something like:
document.pdf<span class="ruFileProgressWrap"><span class="ruFileProgress"></span></span>

to reproduce: 
1. run attached web form. select file for upload. click remove button. view console. all good.

2. click the "delete via api" checkbox to enable. select another file. view console. bad.