Microsoft .NET Runtime 6.0 and
Microsoft ASP.NET Core Runtime 6.0 are system requirements for the File Type Support (FTS) Server, as documented
here.
Your current version of WorldServer needs .NET 6 to run the File Type Support (FTS) Server and Online Editor. So, you won't be able to update it to a higher .NET version at this point.
We will release the next version of WorldServer (11.8.4) around the end of April 2025. This version will support .NET 8.