DVWA COMMAND INJECTION (ALL LEVELS)

A walkthrough of DVWA (Damn Vulnerable Web Application) command injection challenges across all three security levels. At the low level, no input sanitization exists, allowing direct shell command injection via semicolons. The medium level uses a blacklist that strips && and ; but misses the pipe operator |, which can be exploited directly. The high level extends the blacklist to cover most operators but mistakenly only strips '| ' (pipe with space), leaving '|' (pipe without space) fully functional as a bypass. Each level demonstrates why blacklist-based input filtering is fundamentally flawed compared to allowlist or proper input validation approaches.