Hey, this is originally paid method but now provided here for free.

It's bypassing the payment processor with a bug and you can get unlimited amount of items in your cart for free.
Currently have tried it only on Manyvids.

Guide is here:
https://anonymousfiles.io/1N2gthF1/

Code used in Chrome console is here:
https://anonymousfiles.io/JMTMCHnu/