The most significant controversy in the history of Jack in the Box was the devastating 1993 E. coli O157:H7 outbreak caused by contaminated, undercooked hamburger patties sourced from a regional supplier. The outbreak resulted in hundreds of severe illnesses and the tragic deaths of four children, sparking intense public outrage, executive crisis management overhauls, massive lawsuits, and a complete restructuring of the company's food safety standards that permanently reshaped American health regulations.