The script looks like a war bot or how they are called.. They are using known exploid of script (you running Mambo script right?), they google it and then try to inject this script.
Check by running processes (ps) and network connections (netstat) if you are connected to IRC
host: 66.90.88.178
port: 7474
If you are, kill it! and block that port and IP with firewall..
Once you fix this, got to that IRC channel and say to them: I just PWNED YOU!
