Well the vitamin A in it is pretty high, almost impossible to find something thats not a supplement so high in retinol.
I personally doubt the cod liver oil is not rancid the moment you buy it, it is 25% DHA an EPA, 50% mono and 25& saturated.
But the long chain 5 and 6 double bond DHA and EPA are many times as prone to oxidation than the linoleic in linseed which is known to heat u if its oxidizing on air. WAP foundation recomends a teaspoon and that around 1,25 grams of this it. As far as oxidative damage that would equal like 6-10g the seed oil linoleic one.
Its funny Mercola stopped cod liver oil beacuse some weird reason that retinol its no good betacarotene better and reccomend krill oil with only 150 mg DHa and EPA but krill oil also has the antioxidant astaxanthin to stop oxidation. Acoording to his studies the 150 mg krill is better than the 1 gram from cod.
If 150 mg of omega 3 is enough why even take fish oils as far as I know butter has like 150 mg per 50 g and organic one has 3-4 time as much.But t clear the linolenic to DHa enzyme not too much omega 6 needs to be around. Or eat a walnut or two.
Someone like Ray Peat who really limits omega 6 and gets some omega 3 from and dairy fats is probably more "saturated" in omega 3 than people gobbling up fish oils.