On: '; CREATE TABLE `Capture the Flag`; -- Stripe CTF ...

[DanielRibeiro]

, it's often difficult to find a hands-on environment to interact with and fully exploit these vulnerabilities

Well, Google had a good introduction on web exploits, with a sandboxed environment for you to try it: http://google-gruyere.appspot.com/

A bit older, but good nonetheless: Hack this site[1]

[1] http://www.hackthissite.org/

[swores → DanielRibeiro]

The interesting fact about Hack This Site being that it was created and originally run by Jeremy Hammond who was arrested in March for the Stratfor hacking after the FBI had turned 'sabu' to help track others down.