ExecFence catches fake-CAPTCHA "paste this command" scams and warns you before anything runs on your computer.
ExecFence is free on the Chrome Web Store. Open the listing and choose Add to Chrome. Browsers built on Chrome — Microsoft Edge, Brave, Opera, Vivaldi and Arc — install it from the same page. Edge first asks you to allow extensions from other stores; Opera needs its free Install Chrome Extensions add-on.
Open the live demo with ExecFence installed to see the warning fire, and the safe page to see it stay silent.
Does it slow down my browser? No. It checks each page quietly on your own computer and only speaks up when a page shows the scam pattern.
Does it see my passwords or what I copy? It never reads your clipboard or your passwords. When you copy text on a page, it checks that text on your computer for a dangerous command, and never stores or uploads it. See the privacy policy.
It warned on a page I trust. Click the ExecFence icon in your toolbar and choose "Trust this site". On documentation pages you can also turn on Developer mode in its settings, which quiets warnings that are not critical.
How do I report a scam page? In the warning, choose Report. Google Safe Browsing, Microsoft and Netcraft each open their own form in a new tab. Copy report gives you a ready-made summary for the site's host or owner, and it is safe to paste anywhere.