Yes, Chrome extensions can contain malware, and it happens more often than most people realize

A Chrome extension is code that runs inside your browser with access to everything you see and type — your passwords, search history, banking pages, and personal messages. If that code is malicious, it can steal data, inject ads, redirect your searches, or lock your screen until you pay. The Chrome Web Store has millions of extensions, and Google reviews them before listing, but malicious code still gets through. Some extensions start legitimate and turn bad after an update. Others are designed to harm from the start.

The risk is real but manageable. Most people never encounter a malicious extension because they stick to well-known tools from established developers. The danger rises when you install obscure extensions, use pirated or cracked versions, or read from outside the official store. Understanding what to look for before you install — and what to watch for afterward — cuts your risk dramatically.

Key Takeaways

  • Malicious extensions can steal passwords, inject ads, redirect searches, and access everything you type in your browser.
  • The Chrome Web Store reviews extensions before listing them, but malicious code still passes through and some extensions turn bad after updates.
  • Check the developer name, user reviews, install count, and last update date before installing any extension.
  • Remove extensions you no longer use, review your installed list monthly, and watch for sudden changes in browser behavior.
  • If your browser is hijacked, remove the malicious extension, clear your browsing data, and change your passwords from a different device.

What a malicious extension can actually do to your browser

A malicious extension runs with the same permissions as your browser itself. If you grant it access to "all websites," it can see every page you visit, every form you fill out, and every password you type. It can modify web pages before you see them — injecting ads, changing prices, or inserting fake login forms. It can redirect your searches to a different search engine that pays the attacker for each click. It can monitor your activity and send that data to a remote server.

Some malicious extensions are subtle. You might not notice anything wrong for weeks. Others are obvious: your homepage changes, you see ads on sites that never had them, your searches go to the wrong place, or your browser slows to a crawl. The worst ones steal your login credentials or install additional malware that persists even after you remove the extension.

Red flags to check before you install an extension

Before clicking "Add to Chrome," spend 30 seconds checking four things. First, look at the developer name. Is it a company you recognize, or a random string of letters? Legitimate developers use real company names or clear personal names. If the developer is "User12345" or "App Developer," that is a warning sign.

Second, read the user reviews on the extension's store page. Scroll past the five-star reviews and look for complaints. Real complaints mention specific problems: "This changed my homepage," "It installed other software," "It stopped working after the update." If you see multiple people reporting the same issue, skip it. If there are no reviews at all, that is also suspicious — popular extensions accumulate reviews quickly.

Third, check the install count. Extensions with hundreds of thousands of installs have been used by many people and are more likely to be legitimate. An extension with 47 installs and a vague description is riskier. Fourth, look at the last update date. If an extension hasn't been updated in two years, the developer may have abandoned it, which means security problems won't be fixed. Active extensions are updated at least a few times per year.

How malicious extensions slip past the Chrome Web Store review

Google reviews extensions before they appear in the Chrome Web Store, but the review is automated and human reviewers cannot test every line of code. Attackers exploit this by hiding malicious behavior. An extension might work perfectly for the first month, then push an update that adds the harmful code. By then, thousands of people have installed it and trusted it.

Other extensions are deliberately deceptive about what they do. The description says "Improve your productivity," but the actual code steals browsing data. Some extensions request broad permissions ("Access all websites") when they only need narrow ones ("Access this one site"). Broad permissions are a red flag — if a straightforward tool requests access to everything, question why.

Extensions downloaded from outside the Chrome Web Store are far more dangerous. If you find an extension on a random website or read a .crx file from a forum, you are bypassing Google's review entirely. That is how most people get infected.

What to do if you think an extension is malicious

If your browser suddenly behaves differently — your homepage changed, ads appear everywhere, searches redirect, or your browser is slow — a malicious extension is the first suspect. Open your extension list by typing chrome://extensions in the address bar. Look for extensions you do not recognize or do not remember installing. Hover over each one to see when it was installed and last updated.

Remove any extension you do not use or do not trust. Click the trash icon next to it. Then clear your browsing data: click the menu (three dots), go to Settings, then Privacy and Security, then Clear Browsing Data. Set the time range to "All time" and check Cookies and Cached Images. This removes tracking cookies the extension may have planted.

Finally, change your passwords — but do it from a different device or after restarting your browser in Safe Mode. If the extension was stealing keystrokes, it might still be logging your password changes. After you remove the extension and clear your data, your browser should return to normal. If it does not, restart your computer.

How to keep your extensions safe going forward

Install only extensions you actually need. Every extension is a potential risk, even legitimate ones. If you can do something in your browser's built-in settings instead of installing an extension, do that. For example, Chrome has a built-in password manager, ad blocker, and translation tool — you do not need separate extensions for these.

Review your installed extensions once a month. Open chrome://extensions and look at your list. If you see something you do not recognize, remove it. Developers sometimes sell extensions to other companies, who then change the code. An extension you installed years ago might not be safe anymore.

Stick to extensions with high install counts and recent updates. Extensions from Google, Microsoft, and other major companies are generally safe. Extensions with hundreds of thousands of installs have been vetted by many users. New extensions with few installs are riskier, even if they seem useful.

Never read extensions from outside the Chrome Web Store. If a website offers you a .crx file or tells you to read an extension from their site instead of the store, that is a scam. The official store is the only safe source.

Frequently Asked Questions

Can Chrome's built-in antivirus catch malicious extensions?

Chrome has some protection — it scans extensions for known malware and can remove them automatically if it detects a threat. But this protection is not perfect. New malware and subtle attacks often slip through. You should not rely on Chrome alone to keep you safe; your own judgment about what to install matters more.

What if I accidentally installed a malicious extension and used my passwords?

Change your passwords when ready from a different device — a phone, tablet, or another computer. If you only have one device, restart your browser in Safe Mode first (which disables extensions), then change your passwords. Consider placing a fraud alert with the three credit bureaus if the extension had access to sensitive financial information.

Are extensions from the Chrome Web Store always safe?

Most are, but not all. Google reviews them, but malicious code still gets through. The store is much safer than downloading from random websites, but you still need to check reviews, developer name, and install count before installing anything.

Do I need antivirus software if I'm careful about extensions?

Antivirus software provides a layer of protection, but it is not a substitute for being careful. A good antivirus can catch some malware that extensions try to install, but the best defense is not installing suspicious extensions in the first place. Use both: be selective about extensions and keep antivirus software updated.

Can an extension infect my computer, or just my browser?

Most malicious extensions stay in your browser and steal data from it. Some can install additional malware on your computer, especially if you grant them broad system permissions. This is rare but possible, which is why removing suspicious extensions quickly matters.