Why does google say this site may harm your computer?

Lately, all my searches on Google claim in the results that "this site may harm your computer". What's the evidence and why is this coming up?
Update: Apparently, there is a glitch/hacker/virus/malfunction with Google. I saw 600 or more questions just like mine after I posted. I'm sure Google is on it. Thanks all. Glad we're sharing this problem and it's not just me!
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