The Associated Press is reporting that there is a "loophole" that allows people who are suspected of having been Nazi war criminals to collect U.S. Social Security benefits after fleeing the U.S. According to the AP at least 38 suspects are involved. Apparently, these are people who left the U.S. after being threatened with formal expulsion.
I would not call this a "loophole." There is no provision in the Social Security Act that would deny benefits to these people even if they had been convicted of war crimes unless they were actually in prison.
The article is sloppily written or edited. For instance, it keeps using the abbreviation "OSI" without once saying what it means. Apparently, OSI is the Office of Special Investigations at the Department of Justice which seeks out Nazi war criminals living in the U.S. The article talks of "a bitter back-and-forth between the two agencies with each accusing the other of being un-American." However, the article doesn't identify the two agencies. I don't think Social Security was one of those agencies but I can't tell for sure.
By this point, this is mostly of historical interest. The handful of former Nazis involved who are still alive are at least 90. The evidence against them couldn't have been all that strong at the time they left the U.S. or they would have been prosecuted. By this point virtually all witnesses who could testify against them are dead. If some process was created to strip them of their Social Security benefits, they'd be dead before the process could be completed.