For a person belonging to Brazil, it is probably the safest financial product. It would be safer than bonds / equity of any Company.
The only safer alternative could be gold.
If Brazil defaults on its bond obligations, then it will affect everyone. And this includes the Brazilian citizens, who had purchased treasury bonds in the past. In Latin America, there is a tendency to brand the bond holders as rich oligarchs, who are out there to leach the hardworking population. So the majority of the population will support the government, if it decides to default on its bonds.