It is better to have your head in the clouds, and know where you are... than to breathe the clearer atmosphere below them, and think that you are in paradise.
“It's Impossible.” said Pride. “It's Risky.” said Experience. “It's Pointless.” said Reason. If you really are Hacker! then Give it a try!
Using a specially crafted cookie, you can write data to /dev/null. Can you abuse the write and read the flag?
Developers don't always have time to setup a backend service when prototyping code. Storing credentials on the client side should be fine as long as it's obfuscated right?