the President has the discretion to limit reporting of intelligence activities to only eight members of Congress (all of whom, by definition, belong to the two major parties)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.