Hi! I have a question, are web-based games hackable?

I've asked this question on many other hacking forums and all of them told me that it's not possible to hack a web-based game. I really think they are pretty hackable because you can see people getting 72572945683475687346587465874368 gold or w/e in no time. Now, I would like to know if anyone know any hacks/bugs to this addictive web-based game:

www.stratholm.com (It requires an image pack)

Oh, and while you're on it, can you check out this one too?

https://losthope.elixant.net/destiny/ (This one looks pretty vulnerable, does not require any imagepacks. Just register and hack!)

I'll be waiting for your answers.