Forum Getting Re-Directed. Viruses/Malware?

I'm not quite sure how to explain this. This is the first time this has happened to me with my forum and it actually happened once earlier in the morning today and one more time just now. I was on my proboards when all of a sudden I was re-directed to a website called, justbrowsingsearch.com. As soon as I was re-directed to this website, a pop-up appeared in the center of the screen talking about a virus/malware -- just one of those fake pop-ups I'd assume. Is there any reason for this and is there a way that this could be fixed? I don't understand why this happened twice today.

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