Smf 1.1.2 Exploit?

First, I tried putting this in the Website Discussion boards, but it wouldn't let me, and so this seemed like the only other place

Now, my website recently got hacked by some 'Turkish Hackers.' At that time, I was using a few scripts, but one of them was SMF v1.1.2, the latest version as of now. I was very curious how they got in, so I went to Google and typed in ' "SMF 1.1.2" Exploits ', just to see if it was the forum! Then, I found this page!
http://securityreason.com/securityalert/2676

Now, this says something about some login exploit, right? Can somebody please tell me if that is how they may have got into my website, and help me understand how to avoid it in the future? Obviously, I don't want this to happen again. What they did was replace my forum's index.php, and also added a category that redirected to their site in my arcade script (was in a different folder using AV Arcade).

In one of m scripts, I accidentally left the Install.php file in my account. Is this another possible way they got in?

Thanks in advance to any help!