Grab: Arbitary code execution

Grab suffers from arbitary code exeution because it doesn't validate arguments passed to grab.

Proof of Concept:

http://IP/grab?format=jpg&r=10000%20||%20echo%20root:12345%20|%20chpasswd%20||&mode=all&timestamp=12345
Merge pull request #116 from athoik/security-fix

Grab: Arbitary code execution