We are unable to reproduce the problem on our side. However, the information below might be useful:
Sitefinity uses the standard ASP.NET Login control that comes with the .NET Framework. The error comes from FormsAuthentication.Decrypt ASP.NET static method when it is trying to decrypt authentication ticket which is passed as a string.
It is possible that encryptedTicket
string is very long, it is string empty or it is not well formated and it could not be decrypted. ASP.NET uses the <machineKey> element for encryption and decryption of
forms authentication cookie data. By default, both both validationKey and decryptionKey are set to AutoGenerate. There might be a problem if you are running the website in web farm with AutoGenerated keys.
All the best,
the Telerik team
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