Malicious code

I hope this is the right place for this, but I visited one of the HTML pages on my forum and my antivirus software notified me of a threat. I checked the code and noticed there were a few lines of code added to this HTML page that I did not put there. I am the only one that has access to these pages. Any ideas on how this happened and how to prevent it from happening again?

Just remove that code & check.

I removed it and it's fine now, but how did it get there if I didn't put it there? Do you think my account got hacked?

I don't think so, you might have added it by mistake while you added some third party code.

That's what I thought as well. I went to the website that I initially got the third party code to see if those lines were in there and they were not.

Well possibly, can't really confirm what it could have been the cause.

Solved?

Ok, just thought I would ask just in case anyone had ever heard of this happening before. Go ahead and mark this as solved.

Thanks.