Earlier quoted context omitted.
The arguments to controller methods (in CI) are passed through some regular expressions. CI goes as far as to destroy all GET variables (which I highly disagree with).
GET's are all removed (by default), but for uri segments you'll just get some character filters, and some anti-xss attempts (assuming you have that on). Nothing anywhere near sufficient to prevent sql injection. Again, didn't dig too deep, but I don't see any validation that would prevent me from doing some level of at least blindsql..
Any pull request to fix a vulnerability will be happily accepted!