Earlier quoted context omitted.
Yes, but the FBI contains part of the US government's attempts to counter spies and infiltrators, and my understanding is that it's seen as especially important that those people aren't easily bribable.
I would think domestic bribes would be far more likely. Less risk to the agent due to less exposure to a high profile failure. If an agent gets pinched for taking bribes from a business owner or a local sheriff, it's not as big of a scandal as if they took foreign money. And probably easier to set up in the first place.
I don't think the scandal would be the main concern. The main concern would the life imprisonment that treason/spying, when discovered, usually leads to.