Haha. I got 3 cash back rm8, 1 cash back rm88 and 1 cash back rm888. hope to get another cash back rm888. UOB card is great.

5% cash rebate on all online spending except for the following:-
i Insurance including insurance services, insurance continuity or subscription,
insurance sales, underwriting and/or premium;
ii Court costs including alimony and child support; and
iii Government related payments including government fines, government bail
and bond payments and government tax payments.
Note: For the cash rebate category of online spend, the maximum amount of cumulative
cash rebate awarded for both principal and supplementary UOB VOX Card (combined)
is capped at RM50 per calendar month (or such amount that UOBM may decide at its
absolute discretion).

From UOB Website

i have just got the Vox Card too, so far have not made any transaction. hope that i will get 5% rebate on all online transactions except stated above

i think online purchase refers to online transactions which do not require signatures.  I think it includes recurring payments too. Those which are excluded from 5% rebates are Insurance/govt related payments and utilities, MCC 5968. actually i have uploaded the attachment before on the specific MCC codes which do not qualify for 5% rebate. you can search few pages back