When I'm on the forums, sometimes a random window pops up saying: "Install a Java update to continue." Then it take me to a suspicious site and tries to download it, but my virus detector stops it. What is happening?
Does it happen everywhere or only here? If here and elsewhere, you have adware. You can scan your computer for free and remove any adware with Malwarebytes, which I highly recommend.
That's very likely malware on your computer, if you can scan (as recommended by MultiDarkShadow777) then we can rule that out. If it isn't malware then it's potentially caused by a malicious advertisement which we can investigate.
Pictures:
You can just call me Canary.
How not to look like a total fool in the forum games
You can just call me Canary.
How not to look like a total fool in the forum games