The padding oracle challenge has just been the gift that keeps on giving. I wrote a Ruby Gem for exploiting this:

https://github.com/technion/paddingoracle

I've since used it in the wild several times. It is shocking how prevalent the issue is, I suspect because everybody "used a a trusted AES library" and therefore believes they've complied with general crypto recommendations.

Before /r/javascript went private recently I could reply to a post about nearly any project that claimed to use crypto and explain this vulnerability.