MsgCreateTSSVoter::ValidateBasic is lacking validations, for example TssPubkey and KeyGenZetaHeight are not validated at all, and neither inside the handler itself. While I understand this message is restricted to validator, I think you should add more validations as follow.
I would also recommend to go over all the ValidateBasic functions, the implementation is not consistent overall, like not all the message fields are validated inside their corresponding ValidateBasic, some lacking more then others.
https://github.com/code-423n4/2023-11-zetachain/blob/main/repos/node/x/crosschain/types/message_tss_voter.go#L43-L49
