Detect Repeated Url

I hope you can help me with this.

I am using a web security testing application (Golem Technologies) to check if my website is secure. Upon running my site against the test it returned an SQL Injection vulnerability on the following url:

"www.<mysite>. com/www.<mysite>. com/www.<mysite>. com/index.php/\x27\x22

Scan Message: response to \x27\x27\x27\x27\x22\x22\x22\x22 different than to \x27\x22\x27\x22\x27\x22\x27\x22"

when I access the page it simply returned the home page. My question is, how can I throw a 404(Page not found) error for this kind of urls? and why is this not detected by Yii as an incorrect or non-existing path/url?

I also tried to access a non-existing path "www.<mysite>. com/x/y/z/" and it did not return a 404 error.

My website has sub-directories (assets, blog, css, images, protected, and themes).

I will appreciate the help… Thanks.