Browser Passwords Remain Hacker Favorite

You implemented a password manager last year. Your team went through the deployment. IT sent the emails. The training videos got watched. Problem solved, right?

Not even close. While dedicated password managers sat installed on company devices, employees kept right on saving passwords in Chrome, Edge, and Firefox. They did it because browsers made it easy. They did it because nobody told them to stop. They did it because the browser popup appeared every single time they logged into anything, asking if they wanted to save their password. Most people clicked yes.

That decision just cost you everything.

Numbers Tell Uncomfortable Story

At DEF CON 33 in August 2025, security researcher Marek Tóth demonstrated how attackers can steal credentials from password manager browser extensions using a technique called DOM-based extension clickjacking. The vulnerability affected 11 major password managers with a combined 40 million active installations, including 1Password, Bitwarden, LastPass, Keeper, and NordPass. A single click anywhere on a malicious website could expose credit card details, stored personal data, usernames, passwords, and two-factor authentication codes.

But the browser extension vulnerability is just the beginning. The real damage comes from what employees continue storing directly in browsers themselves. According to cybersecurity firm KELA, infostealer malware compromised 3.9 billion credentials from 4.3 million infected devices in 2024. The top three infostealer families, Lumma, StealC, and RedLine, were responsible for over 75% of those infections. Another report from OSIbeyond found that 90% of breached firms in 2024 had credentials leaked and available for sale on dark web marketplaces for just $10 to $15 per account.

Infostealer attacks surged 800% in the first half of 2025 alone. These specialized malware programs target one thing: extracting credentials stored in browsers. They harvest passwords, session cookies, autofill data, and authentication tokens, then disappear before most security tools detect them. A cybersecurity firm found that 21% of its customers' security incidents in 2023 involving unauthorized credential access traced directly to browser credential dumping.

Your browser was designed to render web pages efficiently, not to protect credentials against determined adversaries. The encryption protecting browser-stored passwords can be bypassed with simple command-line scripts requiring no advanced technical skills. Security researchers demonstrated this in under an hour, showing how an attacker with device access can extract every saved password from Chrome, Edge, or Firefox and display them in plain text.

How the Attack Works

Infostealer malware spreads through the same vectors that have worked for decades. Phishing emails deliver malicious attachments. Fake software updates prompt users to download infected files. Compromised browser extensions install backdoor access. Trojanized applications hide malware inside seemingly legitimate programs. Supply chain compromises infect third-party tools and libraries that spread to everyone who downloads them.

Once installed, infostealers need only seconds to execute. They scan the infected device for browser databases storing passwords, cookies, and autofill information. Modern variants target 19 different browsers, from mainstream options like Chrome and Edge to specialized browsers like Tor, Brave, Vivaldi, and Waterfox. The malware executes SQL queries directly against browser databases, extracting website URLs, usernames, and encrypted passwords. It captures clipboard contents, takes screenshots, and harvests Discord tokens. Everything gets packaged and transmitted to remote servers controlled by criminals.

The sophistication level continues rising. RedLine Stealer infected 9.9 million devices worldwide before law enforcement disrupted it in October 2024. Its successor, Lumma Stealer, now dominates the criminal marketplace. These tools operate within a Malware-as-a-Service ecosystem that looks nearly identical to legitimate software businesses. Vendors offer support, automated subscription payments, user dashboards, and affiliate programs allowing other criminals to act as resellers. The barrier to entry is essentially zero. Anyone with cryptocurrency can buy access to enterprise-grade credential theft tools.

The clickjacking vulnerability that Tóth demonstrated at DEF CON adds another attack vector. Malicious websites overlay invisible UI elements on top of seemingly legitimate buttons. When users think they are clicking to close a cookie consent banner or accept a website popup, they are actually triggering password manager autofill functions. The credentials get filled into invisible forms and exfiltrated to attacker-controlled servers. The technique works even when users exercise caution, because they are not clicking on anything suspicious. They are clicking on what appears to be normal website functionality.

Real-World Consequences

In September 2023, attackers used infostealer malware to compromise a multinational corporate computer. The malware harvested passwords stored in web browsers and applications, including credentials for the Regional Internet Registry for Europe, Middle East and Central Asia. Those credentials were exfiltrated and published. The compromised firm did not change the password or implement multi-factor authentication for months, allowing attackers easy access to critical network infrastructure.

The 2023 Okta breach demonstrates how browser password storage creates cascading failures. An attacker stole valid access credentials from an Okta employee who had saved them in their personal Google account while logged in on their Okta-managed laptop. That single credential theft compromised information for every user of Okta's primary customer support system. The attack succeeded not because of a technical vulnerability in Okta's systems, but because an employee stored work credentials in a browser-based password manager synced to a personal account.

In October 2025, researchers at Synthient uncovered a collection of 183 million email passwords exposed through infostealer malware campaigns. The data appeared on the Have I Been Pwned database, marking one of the largest credential leaks of the year. Google confirmed the credentials originated from malware infections on individual user devices, not from any Gmail server vulnerability. The distinction matters. The breach occurred because users stored passwords in browsers, and infostealers harvested them at scale.

According to Verizon's 2025 Data Breach Investigations Report, credentials were involved in 88% of basic web application attack breaches, making them the most common initial attack vector and sometimes the only vector used in an attack. When attackers can simply steal valid credentials instead of exploiting technical vulnerabilities, they choose the easier path every time.

The Defense Contractor Problem

For firms handling controlled unclassified information and working in the defense industrial base, browser password storage creates unacceptable risk. Nation-state actors routinely deploy infostealer malware as part of initial access operations. North Korea's Lazarus group uses RedLine Stealer in its ongoing cryptocurrency theft campaigns. Iranian state-sponsored threat actors have intensified their use of credential theft tools targeting critical infrastructure across healthcare, government, engineering, and energy sectors.

CMMC compliance requires multi-factor authentication and proper credential protection. Storing work credentials in browsers violates the fundamental security principle of protecting authentication data. An estimated 8,350 medium and large defense contractors must implement Level 2 third-party assessments. Those assessments evaluate whether security controls actually protect sensitive information, not just whether the controls exist on paper.

No compliance framework will protect you if your employees store passwords in browsers that malware can harvest in seconds. The regulation requires MFA and credential protection. It does not prevent infostealer malware from extracting browser-stored passwords before MFA even becomes relevant. You can pass the assessment and suffer a breach the same day using attack vectors your security architecture completely ignores.

Why Traditional Approaches Fail

Most firms approached browser password storage as a training problem. Send the emails. Create the awareness campaigns. Tell employees not to save passwords in browsers. Hope they listen. That approach failed because it depended on perfect human behavior under imperfect conditions. Browsers prompt users to save passwords automatically. The popup appears every single time someone logs into anything. Declining the prompt requires active effort. Accepting it requires one click. Over months and years, that friction wears people down.

Implementing a dedicated password manager does not solve the problem unless you also remove existing credentials from browsers. Employees who transitioned to proper password managers often left their old browser-stored passwords in place. They used the password manager for new accounts while continuing to autofill old credentials from the browser. Security teams assumed deployment meant adoption, but deployment only means the tool exists. Adoption requires removing the alternative.

The clickjacking vulnerability affecting password manager extensions reveals another uncomfortable truth. Even firms that mandated dedicated password managers remained vulnerable if those managers operated as browser extensions. The fundamental issue is that browsers were not designed as security platforms. They prioritize user experience and convenience. Extensions inherit those same priorities and constraints. Security requires architecture designed specifically for protecting authentication data, not features bolted onto systems built for other purposes.

What Actually Works

Active Directory group policies combined with application allowlisting tools can block browser password storage at the system level. Configure Windows Defender Application Control or similar tools to prevent browsers from accessing or creating password database files. This removes the ability to store credentials regardless of user behavior. The technical control eliminates the vulnerability instead of asking employees to avoid it.

Deploy an enterprise password manager with mandatory usage policies. Keeper, 1Password, Bitwarden, and Dashlane all provide centralized management, policy enforcement, and audit trails showing who accessed what credentials and when. These tools use encryption keys derived from master passwords that never leave user devices. They require explicit authentication before revealing any saved credentials. An attacker who compromises a device still cannot access the password vault without additional authentication factors.

Schedule mandatory password migration sessions where IT staff actively remove every saved password from every browser on every device. Do not send instructions for employees to do this themselves. Do it for them. Export existing credentials from browsers into the password manager, verify the migration succeeded, then delete every browser-stored credential. This cannot be optional. This cannot be self-service. This must be enforced systematically across the entire firm.

For browser extension-based password managers, reconfigure site access settings to require manual interaction. On Chromium-based browsers like Chrome and Edge, navigate to extension settings, select site access, and choose the on-click option. This prevents the extension from autofilling credentials unless the user explicitly clicks the toolbar icon. The additional step blocks clickjacking attacks that rely on invisible autofill triggers.

Implement continuous monitoring for stolen credentials appearing on dark web marketplaces. Services from firms like Flare, SpyCloud, and KELA scan criminal forums, paste sites, and infostealer logs for your company's email domains and credentials. When employee credentials surface for sale, you receive alerts within hours. Force immediate password resets for compromised accounts, terminate active sessions, and scan the affected device for malware. Speed matters because attackers typically exploit stolen credentials within hours of purchase.

Deploy endpoint detection and response tools specifically configured to detect infostealer behavior patterns. Modern EDR solutions can identify the SQL queries infostealers execute against browser databases, unusual network traffic exfiltrating large credential files, and the specific API calls malware uses to access password storage locations. Configure these tools to alert on suspicious activity and automatically isolate compromised endpoints before data leaves your network.

Industrialized Credential Theft

Browser password storage represents a critical vulnerability that most firms continue ignoring despite trivial remediation requirements. You spent money deploying password managers. You spent time training employees. You checked the compliance boxes. None of that matters if browser-stored credentials remain accessible to malware that harvests them in seconds.

Attackers have industrialized credential theft. Infostealers operate as Malware-as-a-Service businesses with subscription pricing, vendor support, and affiliate programs. The criminal marketplace makes enterprise-grade attack tools available to anyone with cryptocurrency. Your adversaries are not checking whether you are compliant. They are checking whether credentials exist in browsers where malware can harvest them.

The solution requires two actions: implement a proper password manager and remove all credentials from browsers. Neither action requires advanced technical expertise. Neither action costs significant money. Both actions deliver immediate, measurable risk reduction. What stops most firms is not technical capability or budget constraints. What stops them is treating this as an optional improvement instead of a critical vulnerability requiring immediate remediation.

We covered this topic in March 2025 when we published our guide on removing browser passwords. Eight months later, the threat landscape has gotten worse. Infostealer infections surged 800% in the first half of 2025. The DEF CON vulnerability demonstrated that even dedicated password manager extensions remain vulnerable to sophisticated attacks. Credentials worth billions of dollars circulate on criminal marketplaces, available for purchase at $10 to $15 per account.

Your people will continue saving passwords in browsers until you remove the capability. Training does not overcome convenience. Policies do not overcome automatic prompts appearing hundreds of times per month. Technical controls overcome vulnerabilities by eliminating the attack surface. Deploy the password manager. Migrate the credentials. Delete everything stored in browsers. Configure the policies to prevent future storage. Monitor for compromised credentials. Act when they appear.

The attackers have the tools. They have the infrastructure. They have the patience. What happens next depends on whether you fix this vulnerability before they exploit it. Take a hard look at your authentication architecture this week. Schedule the browser password migration sessions. Implement the technical controls that make credential theft exponentially harder. Do something today that makes your firm more secure than it was yesterday.

Stop asking employees to remember not to save passwords. Stop hoping they will decline the browser prompts. Stop treating convenience features as security solutions. Build systems that do not depend on perfect human judgment under constant friction. Your credentials are already circulating on criminal marketplaces. The question is whether you will fix the vulnerability before the next breach or after.

The threats are real. The data is clear. The solutions exist. What happens next is up to you.

Need Help Deploying a Password Manager?

STACK Cybersecurity provides live onboarding sessions for clients deploying password managers. We handle the technical migration, ensure complete credential removal from all browsers, and train your team on secure password management practices. Contact us to schedule your onboarding session and eliminate this vulnerability before an attacker does it for you.

Call (734) 744-5300 or Contact Us to schedule your Keeper Password Manager onboarding session.

Works Cited

1. Socket. "DOM-Based Extension Clickjacking Exposes Popular Password Managers to Credential and Data Theft." Socket Blog, August 2025. https://socket.dev/blog/password-manager-clickjacking

2. eSecurity Planet. "3.9 Billion Passwords Compromised by Infostealer Malware." eSecurity Planet, February 27, 2025. https://www.esecurityplanet.com/cybersecurity/data-theft-infostealer-malware-2025/

3. OSIbeyond. "Infostealer Malware: The Silent Threat to Your Digital Credentials." OSIbeyond Blog, August 15, 2025. https://www.osibeyond.com/blog/infostealer-malware-the-silent-threat-to-your-digital-credentials/

4. Bank Info Security. "Alert: Info Stealers Target Stored Browser Credentials." Bank Info Security, March 1, 2024. https://www.bankinfosecurity.com/alert-info-stealers-target-stored-browser-credentials-a-24490

5. Verizon. "2025 Data Breach Investigations Report." Verizon Business, 2025. https://www.verizon.com/business/resources/reports/dbir/

6. STACK Cybersecurity. "How to Remove Browser Passwords for Heightened Security." STACK Cybersecurity Blog, March 11, 2025. https://stackcybersecurity.com/posts/howto-remove-browser-passwords