Nasty stuff. Decades ago at an outdoor work party on a Saturday afternoon we had about 100 people there, no more than half of them showed up at work Monday and we weren’t really back to normal until Thursday. Some were hospitalized. I was young then and choose to rough-it by not going to the hospital, and it was bad.
We traced it to mayonnaise, which was in the macaroni salad. The weather was hot that day and it only takes a very short time for the microbes to reach critical mass in mayonnaise when conditions are right, and you WILL NOT notice any change in taste - the stuff tasted great.
So I am very leery about anything with mayonnaise where I can’t be sure of the history of it. If it’s a restaurant, for example, it’s probably ok. Same with a buffet if it’s cold (as in refrigerator temperature). But a party, any party, that isn’t professionally catered - no thanks, I’ll find something else to eat.
I leave mayonaisse in the sun before eating it.