Freedom United has highlighted an article by The Guardian about the plight of foreign national workers in embassies in Australia. Although Australia has rules and, supposedly, oversight to prevent the exploitation and abuse of foreign domestic help by those with Diplomatic Immunity, the Salvation Army Freedom Partnership says they generally help about three slavery victims a year. That is the number that is actually able to reach an outside person and ask for help. Based on the circumstances of their captivity there is a good chance that more are also being exploited inside embassies but are entirely prevented from interacting with anyone who can get help.
This isn't a problem just in Australia. The US has also had cases of domestic servants brought to their national embassies under contracts that were promptly ignored while the workers were unpaid and forced to work endlessly under threats to their families back home. Unfortunately, as long as the doctrine continues that an embassy is technically the ground of the visiting nation (which we benefit from as well), it is uncertain if there is a solution.