Why do I need to complete a CAPTCHA?
Completing the CAPTCHA proves you are a human and gives you short-lived access to the web property.
What can I do to avoid this in the future?
If you are on a personal connection, like at home, you can run an anti-virus scan on your gadget to ensure 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 searching for misconfigured or contaminated gadgets.
Another way to prevent getting this page in the future is to use Personal privacy Pass. You might need to download variation 2.0 now from the Firefox Add-ons Shop.