Telerik.Web.UI in Progress Telerik UI for ASP.NET AJAX before R1 2017 and R2 before R2 2017 SP2 uses weak RadAsyncUpload encryption, which allows remote attackers to perform arbitrary file uploads or execute arbitrary code.
https://unit42.paloaltonetworks.com/silent-skimmer-latest-campaign/
https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2018-0006
http://www.telerik.com/support/kb/aspnet-ajax/upload-%28async%29/details/unrestricted-file-upload