Rails bug in versions 1, 2, and 3

Want to know how to raise a 500 error in any version of rails (so far)? Simply add ?a&a[] to the end of any URL in any Rails application.

I tested this on a number of known rails sites such as Chargify, Twitter, Groupon, Hoptoad (oh the irony), and even a Rails v1 website somebody managed to find.

For such an old bug (essentially as old as it can be), it’s quite funny that it was apparently patched less than two weeks ago.