1: that's not "absolutely zero oversight"
2: It seems like a reasonable way to maintain critical secret information while still informing members of the opposition party. That means at least several of these members are being briefed:
Dianne Feinstein - California
Ron Wyden - Oregon
Martin Heinrich - New Mexico
Angus King - Maine
Kamala Harris - California
Michael Bennet - Colorado
If something goes totally off the rails they can provide oversight.
Historically, that's not true at all. I was going to give a list of cases of egregious actions by the CIA, but quickly realized I'd be sitting here all night if I really wanted to put together any halfway complete list. The sheer number of coups, assassinations, drug-running operations, weapons smuggling operations, etc. that the CIA has run is just mind-boggling. The list of countries that haven't had a CIA-backed coup or insurgency might be shorter than the list of countries that have. Things "go off the rails" so often with the CIA that going off the rails seems to be the plan.