There is no authorised domestic retail forex or CFD market in Brazil. The CVM regulates securities and licensed intermediaries, and it has not built a framework for retail CFDs, so brokers offering them to Brazilians are operating offshore and outside CVM authorisation. The commission routinely issues investor alerts naming firms that solicit Brazilian residents without permission, and it has imposed stop orders and settlements in the past.
Trading with an offshore broker is generally not treated as a crime for the individual, but it sits in a grey area with little local recourse. If a bonus dispute or a withdrawal problem arises, the CVM cannot help you against a firm it never authorised. That shifts all of the protection onto the broker's foreign licence and your own checks.
If you do proceed, treat the broker's offshore regulation as the only safety net and read it carefully. Confirm which entity holds your account, check whether the firm appears on a CVM alert list, and test that withdrawals in reais clear before you let any bonus turnover lock up your funds.