According to https://github.com/dotnet/designs/blob/master/accepted/2020/better-obsoletion/obsoletions-in-net5.md, .NET 5 will obsolete the UTF-7 encoding:
The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead.
- DiagnosticId: SYSLIB0001
- APIs:
- System.Text.UTF7Encoding (constructors)
- System.Text.Encoding.UTF7
According to https://github.com/dotnet/designs/blob/master/accepted/2020/better-obsoletion/obsoletions-in-net5.md, .NET 5 will obsolete the UTF-7 encoding: