Your Website is vulnerable.
My name is Andy, I am a white-hat hacker. I look for vulnerabilities on peoples websites and help them to fix the problem before someone else comes along and does damage to the site. I found the vulnerability on your site a while back.
If an admin would like to get in contact with me to fix the problem please let me know and i will give you my contact details.
Note: If you think I'm some kid lying to you, ban me and see what happens.