First time I took part in one of these challenges and I enjoyed it a lot. I made it only up to level 3 and seeing comments of others at higher levels saying it was easy, wasn't very good for my self-confidence :-) However, I can only assume they had some prior experience in this field and / or had an IQ of 150 (http://abiusx.com/stripe-ctf-2-web-challenges/).

After having spent more than a day on level 3 I decided to look on-line for solutions and came across the aforementioned website. I was happy to see my attempt was pretty close but looking at the rest of the levels it was obvious I was out of my depth and gave up (it was already Tuesday anyway).

These write-ups are nice (although abiusx' ought to have been posted only after the challenge was finished) to see how others have solved the levels in different ways.

I can't wait for the next challenge from Stripe and will definitely check out some others on-line. It's like puzzles for grown men.