If you are using Google Chrome or a third party browser that uses the Chrome engine, then this is likley to be a bot that Google have to detect what they term as unsafe sites, there should be a link on the red warning or an email address, read the riot act to google as they are messing with you for trying to keep this secure, and because their bots can’t crawl all over the SC app, it repots it as a dangerous site.
Get the client to contact their hosting service and they will also contact Google. I had same issues got it fixed within the hour, Googel treading a very fine line.