I put uncooked hot peppers in olive oil with garlic, onions, and seasoning. When I opened the jars, they fizzled. Is this safe to eat?
Without further ado, that’s an indication of biological activity. Both garlic and hot peppers are used for making fermented hot sauce, but using specific recipes known to (or designed to) stop pathogen growth.
I believe your intention was to infuse the olive oil with hot pepper and garlic aroma, it looks like it didn’t go well as some biological activity took place. I don’t think at this point you can be really sure what was growing inside the jars.
Taking the presence of raw garlic into consideration, and the oxygen-free environment created by the garlic being submerged in the oil, I’d be scared of a potential botulism pathogen growth as the olive oil itself won’t be enough to inhibit the growth of such pathogens. And raw garlic can host such bacteria.
And as a general rule:
When in doubt, you should discard it.
I would go a step beyond @zetaprime: Oil is the perfect, preferred environment for botulism. Garlic and onions are low acid roots and have a high probability of exposure. Peppers and spices are also normally low acid and considered potentially exposed. USDA recommendations are refrigerate at low temperature, lower than most home units, and use within 4 days to slow potential growth or freeze, never can and leave at room temperature.
People often point to commercially canned garlic in oil and herb infused oils. Those items have typically been pasteurized, and always acidified to make them safe even at room temperatures. They are not the same as what you can make at home.
Finally, any hissing, bubbling, or other signs of off gassing such as a bent lid is a sure sign of potentially deadly bacterial action. You have a presumably sealed environment and yet gasses are being produced. They have to come from somewhere. It could be a chemical reaction, fermentation, or bacterial, but none of those sources is intended or likely to be desired and could be far worse than just a poor product. The absence of such activity is not a sign of safety, but the presence should always be considered a sure sign that it is not safe. This was considered true long before the USDA started publishing stricter guide to home preservation: when our grandparents would regularly reuse mayonnaise jars and lids, and trim half spoiled fruit. If they saw signs of gas, they assumed it was bad and tossed it.