That Chrome Extension You Trust? It Might Be Stealing Everything You Type

You probably have at least ten browser extensions installed right now.

Maybe a password manager. An ad blocker. A productivity tool. A grammar checker.

They all look harmless. Some even have "Featured" badges from Google. Millions of people use them every day.

And some of them are stealing your passwords, your bank logins, and your private conversations without you ever knowing.

This isn't a hypothetical threat. In 2025, over 8.8 million users were affected by a single campaign that turned trusted extensions into spyware. The attackers had been building trust for seven years before flipping the switch. (The Hacker News)

Welcome to the era of Malware-as-a-Service browser attacks.

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Table of contents

• The threat nobody saw coming
• What is Malware-as-a-Service and why it matters
• How criminals weaponize browser extensions at scale
• The sleeper agent problem: trusted extensions turn rogue
• Real attacks that hit millions of users in 2025
• Why your current security tools cannot stop this
• How RedPhish defends against MaaS browser threats
• What you can do today to stay safe

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The threat nobody saw coming

Browser extensions are trusted. They have "Featured" badges. They have millions of downloads. And they are stealing your data right now.

A single campaign called DarkSpectre affected 8.8 million users across Chrome, Edge, and Firefox. The attackers spent seven years building trust before weaponizing their extensions. (The Hacker News)

This wasn't a bug or an accident. It was a business.

Criminal organizations now sell complete attack kits that anyone can use. No coding skills required. You just pay a fee and get access to malware, infrastructure, and support. Security researchers call this Malware-as-a-Service, or MaaS.

MaaS has made it easy for anyone to launch sophisticated browser attacks. The results are showing up in headlines every week.

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What is Malware-as-a-Service and why it matters

Think of MaaS like renting an apartment instead of building a house.

Malware-as-a-Service is a business model where criminals provide access to malicious software and infrastructure for a fee. It works just like the legitimate software subscriptions you use every day. (Check Point)

The MaaS model has lowered the barrier to entry for cybercrime. Even people without coding or technical skills can now carry out complex attacks. Operators provide ready-made malware, hosting, and customer support. (Check Point)

The numbers tell the story.

Check Point's 2025 State of Cyber Security Report found that global attacks against organizations increased by 44% in the last year. When it's easy to launch attacks, more attacks happen. (Check Point)

Researchers found 384 unique malware variants sold across the top three criminal forums in 2024. That's a 10% increase from the previous year. (Bitsight)

Infostealers are the fastest growing malware category in 2025. These tools grab your passwords, session cookies, and browser data. According to the 2025 Verizon DBIR, 32% of breaches globally involved stolen credentials. Many came from infostealers. (Pen Test Partners)

Browser extensions are the perfect delivery vehicle for MaaS attacks. One compromised extension can reach millions of users instantly.

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How criminals weaponize browser extensions at scale

The playbook is surprisingly simple.

Step one: build trust. Criminals publish a useful extension that does exactly what it promises. Maybe it blocks ads. Maybe it helps with screenshots. Maybe it enhances video playback. It works perfectly for months or years.

Step two: grow the user base. The extension earns positive reviews. It gets featured in the Chrome Web Store. Millions of people install it because it looks legitimate. Because it is legitimate, at first.

Step three: flip the switch. One day, the extension pushes a silent update. Users don't notice because browser extensions update automatically in the background. But now the code includes spyware, data stealers, or backdoors.

This approach works because of how browser extensions function. They have access to everything you do online. They can read your passwords. They can modify web pages. They can track every site you visit.

Security expert Jamie Blasco told Dark Reading why this matters: controlling an extension gives attackers a powerful vantage point for all browser activities. (Dark Reading)

One developer compromise can reach hundreds of thousands of machines instantly. You only need to fool one person to get access to millions.

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The sleeper agent problem: trusted extensions turn rogue

Security researchers have a name for this pattern. They call them "sleeper agents."

These are extensions that operate cleanly for years before being weaponized. The developers earn trust, build up millions of installs, and even collect "Featured" or "Verified" badges. Then they push silent updates that turn their add-ons into spyware. (Dark Reading)

In one campaign, researchers found five extensions that ran clean for years before going rogue in mid-2024. The long game paid off. By the time the malware activated, the extensions had millions of trusting users. (Dark Reading)

There's another variation that's even scarier.

Security researchers at SquareX Labs discovered "polymorphic" extension attacks. These allow malicious extensions to impersonate other extensions on your browser. The fake extension can look exactly like your password manager, crypto wallet, or banking app. (Bleeping Computer)

You think you're entering your master password into 1Password. You're actually handing it to attackers.

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Real attacks that hit millions of users in 2025

These aren't theoretical threats. Real attacks hit real people throughout 2025. Here are the biggest ones.

DarkSpectre: 8.8 million victims over seven years

A Chinese threat actor ran three connected campaigns called ShadyPanda, GhostPoster, and DarkSpectre. Together, they affected over 8.8 million users of Chrome, Edge, and Firefox. (The Hacker News)

The attackers played the long game. They published harmless extensions and let them run clean for years. This built trust and user bases. Then they pushed malicious updates that turned the extensions into spyware with backdoor capabilities. (Dark Reading)

Cyberhaven supply chain attack: 2.6 million exposed

On Christmas Eve 2024, attackers phished a Cyberhaven employee and got access to the Chrome Web Store. They published a malicious version of the company's extension. The security team found and removed it within 60 minutes, but damage was done. (Cyberhaven)

Researchers discovered the attackers had compromised more than 30 other Chrome extensions. Over 2.6 million users were affected. The attackers targeted Facebook Ads accounts to run fraudulent campaigns. (Darktrace)

AI chatbot data theft: 900,000+ users

Two malicious extensions stole ChatGPT and DeepSeek conversations from over 900,000 users. The extensions were named "Chat GPT for Chrome with GPT-5, Claude Sonnet & DeepSeek AI" with 600,000 installs and "AI Sidebar with Deepseek, ChatGPT, Claude, and more" with 300,000 installs. (Dark Reading)

They requested permissions under the guise of collecting "anonymous, non-identifiable analytics." In reality, they were stealing every conversation you had with AI tools.

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Why your current security tools cannot stop this

If these attacks are so common, why doesn't your antivirus catch them?

The answer is simple. MaaS attacks are designed to evade traditional defenses.

Since MaaS enables endless malware customization and variation, traditional antivirus signatures struggle to detect them. By the time a signature is created, attackers have already created new variants. (Check Point)

Extensions also operate in a blind spot.

Most security tools run on your device, not inside your browser. They scan files and monitor network traffic. But malicious extensions operate after encryption and after authentication. They often don't drop any files for endpoint tools to scan. (Dark Reading)

Auto-updates make it worse. Extensions update silently without asking permission. An extension that was safe yesterday can be malicious today. Your security software has no way to know.

The "Featured" badge creates a false sense of security. But Chrome Web Store approval isn't a guarantee of safety. Sleeper extensions pass every review because they're actually legitimate until they're not.

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How RedPhish defends against MaaS browser threats

RedPhish takes a different approach to browser security. It runs inside the browser where attacks actually happen.

Traditional security runs on the endpoint. RedPhish runs in the browser. That's the difference that matters.

Real-time URL scanning

RedPhish checks URLs before pages load. This catches malicious redirects and phishing pages that extensions might inject. The scanner uses a 24-hour persistent cache with 50,000 URL capacity for fast lookups.

When a compromised extension tries to redirect you to a credential harvesting page, RedPhish blocks it before you see the trap.

ClickFix malware detection

Many MaaS campaigns use social engineering to trick users into running malware. RedPhish detects fake CAPTCHA prompts and verification screens that try to make you execute code. It uses a scoring system to identify these attacks and blocks them before they can execute.

Credential theft protection

RedPhish identifies phishing pages designed to harvest your passwords. If a malicious extension redirects you to a fake login page, RedPhish recognizes the threat and blocks it.

Malvertising and ad blocking

Malicious extensions sometimes inject ads or fail to block dangerous ones. RedPhish blocks malicious ads and removes tracking scripts that steal browsing data.

Card skimmer protection

RedPhish detects JavaScript skimmers on checkout pages. Even if a malicious extension injects payment theft code, RedPhish catches it.

Cryptominer blocking

Some malicious extensions run mining scripts that drain your device resources. RedPhish uses network-level blocking to stop them.

Why browser-level protection matters

Other browser extensions can be compromised. That's the whole problem this post describes. RedPhish uses privacy-first design with no data retention. Behavioral detection catches variants that signature-based tools miss.

RedPhish works alongside endpoint protection, not instead of it. You need both layers to stay safe.

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What you can do today to stay safe

MaaS browser extension attacks aren't going away. They're getting worse because they work.

Here's how to protect yourself.

1. Audit your browser extensions right now

Open your browser's extension settings. Look at every extension installed. Ask yourself: do I actually use this? If not, remove it.

2. Remove any extension you don't actively use

Every extension is a potential attack surface. Fewer extensions mean fewer risks. Keep only what you truly need.

3. Check permissions carefully

If a simple screenshot tool wants to "read and change all your data on all websites," that's a red flag. Extensions should only request permissions they actually need.

4. Don't trust badges alone

"Featured" and "Verified" badges don't mean an extension is safe. Sleeper extensions earn these badges before going rogue. Treat every extension with healthy skepticism.

5. Install browser-level protection like RedPhish

You can't manually review every extension update. You can't spot every polymorphic attack. Browser security tools exist because humans can't do this alone.

RedPhish detects malicious behavior in real time, right where attacks happen.

6. For businesses: use enterprise policies

If you manage devices for a team, use browser policies to whitelist approved extensions. Block unknown extensions entirely. This prevents employees from accidentally installing compromised tools.

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The bottom line

Browser extensions have become the new frontier for cybercrime.

MaaS has made it easy for anyone to launch sophisticated attacks. Sleeper extensions build trust over years before going rogue. Millions of users have already been hit by campaigns they never saw coming.

Traditional security tools can't stop these attacks. They run on endpoints, not in browsers. They use signatures, not behavioral analysis. They're blind to the threat.

RedPhish protects where it matters. Inside your browser. In real time. Before attacks can steal your data.

You shouldn't need a security degree to browse safely. Install RedPhish and let it handle the threats so you can focus on your work.