There is a script tag that is almost certainly the cause of the alert (see image1) and it is using an obfuscated domain, hXXp://%63%2E%6Ej%652.c%6E this is a Chinese domain (see image2) and is malicious as avast also alerts on it, see image3.
So it looks like this page owners/userindex.aspx if not other areas of the site has been hacked.
Please remove or modify the script tag, that was the whole point of my placing it as an image, so as not to place code in the forum to avoid any possible detection by avast in its own forum.