An All New Rails Security Guide
railsinside.com
railsinside.com
Generally I think this particular guide is satisfactory on details but very poor on structure. For instance, it starts the section on SQL Injection off by saying that Rails is mostly immune to it, due to clever design choices. Nonsense. The same corner cases that cause all modern apps to still have SQLi apply to Rails as well --- sort columns on tables, query builders, and everything else that requires you to concatenate SQL expression tokens instead of using stored procedures. If you con yourself into believing Rails protects you from this, you're the dev who's going to wind up with the Rails SQLi vulns.
Not a particularly big fan of their coverage of session security, either: a passing mention of httpOnly, just enough to give people the impression that it does something that it doesn't do, but a total miss on something that is going to cause Rails devs to fail PCI audits: poor domain scoping on cookies and lack of the "secure" flag.
if only there were some sort of wiki where all these ad-hoc Rails security guides could be coalesced. hmm, what to do.