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What can I do to prevent this in the future?
If you are on a personal connection, like at home, you can run an anti-virus scan on your device to make sure it is not contaminated with malware.
If you are at an office or shared network, you can ask the network administrator to run a scan across the network trying to find misconfigured or contaminated devices.
Another method to avoid getting this page in the future is to use Privacy Pass. Take a look at the browser extension in the Chrome Web Shop.