All your investments are held at the custodian accounts maintained by the transfer agents of the individual fund houses (e.g. Fidelity, Invesco etc.). Your uninvested cash balances are kept in a segregated client funds account at HSBC Hong Kong, regulated by the Hong Kong Monetary Authority. These entities are regulated and have proper security measures to protect your assets.
Your money and assets are kept separately from the Endowus company assets as required by the Securities and Futures Commission of Hong Kong.