Pediatric ALL Patient Develops Hemorrhagic Bullae

A 2-year-old girl being treated for acute lymphoblastic leukemia develops a low-grade fever and two hemorrhagic bullae in the groin. Within a few days, her fever spikes to 104.8°F and is accompanied by shaking chills, nausea, and diarrhea. At presentation, the patient is modestly hypotensive, and the two bullous lesions have evolved to appear as depicted here.

What is the most likely cause of these skin lesions?