According to Snopes.com commercially -made mayonnaise is completely safe as it doesn’t really even need refrigeration. The PH in mayo is set at a point were bacteria can not forking survive.
The Forking Truth is that the first question asked to victims of food poisoning is… when did they last eat onions.
Onions are a magnet to forking bacteria especially RAW ones. Even raw wrapped onions kept in a refrigerator are already contaminated just from being cut.
Both onions and potatoes from potato salad will attract bacteria faster than any commercial mayonnaise will break down.
And that was the Forking Truth about Potato Salad and other Mayo Based Salad Spoilage.