Security Basics: about SQL injection

[Seung Hyun Cho <s970501 () gmail com>]

Hi,

I am running my site on IIS & MS-SQL.

I've found vulnerabilities in some pages.
exploited query is working like...
"select * from xxx where id=3"
when I put something like '2 or 1=1', it shows every data in xxx.

But... is it kind of big vulnerability?
What hacker can do to my site in this situation?

Thanks,

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