ServiceStack before 5.9.2 mishandles JWT signature verification unless an application has a custom ValidateToken function that establishes a valid minimum length for a signature.
forums.servicestack.net/t/servicestack-v5-9-2-released/8850
github.com/ServiceStack/ServiceStack/commit/540d4060e877a03ae95343c1a8560a26768585ee
www.shielder.it/advisories/servicestack-jwt-signature-verification-bypass/
www.shielder.it/blog/2020/11/re-discovering-a-jwt-authentication-bypass-in-servicestack/