Press Command + Option + Esc and Force Quit the browser.
If you encounter one of these, Not even the "Close" or "Cancel" button, as these are often masked links that trigger a download. Force Quit Your Browser: phishing pop ups
This is the most common variety. The pop-up claims your Windows or macOS system has been locked due to suspicious activity. It provides a "toll-free" number for Microsoft or Apple Support. Press Command + Option + Esc and Force Quit the browser
Phishing pop-ups (also known as "tech support scams") are deceptive browser alerts designed to trick you into calling fake support numbers, downloading malware, or providing sensitive data. 1. How to Spot a Phishing Pop-Up The pop-up claims your Windows or macOS system
A phishing pop-up is a malicious browser window that appears suddenly, intended to trick the user into revealing sensitive information, paying for fake services, or downloading malware.