They were developed and coded by someone so how can you be so sure that "someone" hasn't left any backdoors?

Open source code.
Heads up 300+ Coin Wall @ $16,654 on BitFinex (i know we follow stamp here but.......)
Was put up for 10 secs and pulled down then back up and back down.....
Whats with this ontopic nonsense?
I was thinking the exact same thing when OBSERVING THE WALL! Crazy to think that still happens here!