Russians, Iranians, and Chinese spark security fears after taking $100,000 shortcut for citizenship in a Caribbean paradise

• "Golden passports" let foreigners acquire citizenship in exchange for investing in certain countries. 
• Citizens of some Caribbean nations have been able to visit the EU without visas since 2015.
• The European Union may crack down on visa-free travel after revealing the scale of the passport trade.  

Tens of thousands of passports have been obtained by Russians, Iranians, Chinese and others from Caribbean nations, granting them visa-free travel to European countries, according to a report by the European Commission.