Hello,
After verification, the current version of the SagePay plugin is fully compatible with the 3D Secure authentication.
It uses the "Form Integration" which provides the necessary for the 3DSecure.
The "Direct Integration" is also compatible with the 3D Secure but it allows the customer to stay on the HikaShop website without the need of a redirection to the SagePay platform.
So, in any case, it's good !
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.