This case demonstrates a classic but still deeply effective tactic: the use of an improperly validated file upload to implant a web shell. It wasn’t an exploit. It wasn’t a brute force attack. It was a misused feature — a vulnerable application logic path that let an attacker turn a web server into a foothold.

From access logs to file integrity alerts, from PHP function calls to backend cron jobs, this case demands investigation across both the application and the host layers. It also highlights the critical need for defense in depth:

Proper upload validation (MIME type, content inspection)

Disabling script execution in upload directories

Continuous file integrity monitoring

Detection of command execution and outbound network anomalies