Using a heuristic system to detect an anomaly in a computer's baseline, a system administrator was able to detect an attack even though the company signature based IDS and antivirus did not detect…

Using a heuristic system to detect an anomaly in a computer's baseline, a system administrator was able to detect an attack even though the company signature based IDS and antivirus did not detect it. Further analysis revealed that the attacker had downloaded an executable file onto the company PC from the USB port, and executed it to trigger a privilege escalation flaw. Which of the following attacks has MOST likely occurred?