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Google Finds 316,000 Accounts Using Logins From Past Breaches

Google's findings are based on a free Chrome extension it released in February called Password Checkup, which will alert you when your password choice was previously found in a past data breach.

 & Michael Kan Principal Reporter

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New research from Google has found that "security conscious" consumers are avoiding easily guessable passwords and using unique ones for their web logins. Nevertheless, there are still hundreds of thousands of accounts out there using login credentials that have been exposed in past data breaches.

Google's findings are based on a free Chrome extension it released in February called Password Checkup, which will alert you when your password choices are weak. The extension does this by checking your logins against a database of 4 billion usernames and passwords found in past data breaches.

More than 667,000 users installed the extension in the first month after it launched. Google's security researchers then took anonymized data from the Password Checkup extension to examine the scale of vulnerable web logins.

"In the first month alone, we scanned 21 million usernames and passwords and flagged over 316,000 as unsafe," Google's security researchers wrote in a blog post on Thursday. That amounts to 1.5 percent of the sign-ins being vulnerable to "credential stuffing" attacks, in which hackers use an automated technique to plug in previously leaked passwords to break into the victim's account.

Google Credential stuffing

Fortunately, Google's extension was able to alert the affected users about the vulnerable passwords. But despite the warnings, the users didn't always change their logins. The company's researchers only found that 26 percent of the alerted users migrated to a new password that was generally as strong as the original password or stronger.

Other users chose to ignore the warnings from the extension, possibly because the affected account had little value, or because the users lacked full control of the account, the researchers speculated in a paper about their findings, which was written jointly with experts at Stanford University.

The 1.5 percent figure is actually lower than what a 2017 Google study found; it estimated that 6.9 percent of Google users were vulnerable to account hijacking from passwords exposed in previous data breaches. "Possible reasons [for the discrepency] include the user population that adopted our extension is more security conscious —thus avoiding reuse as a behavior," the researchers said in their paper.

The examined web logins also only covered a one-month period. As a result, it's possible users never signed into dormant or older web accounts, which are generally registered with weaker login credentials.

Google's security researchers say they'll continue refining the Password Checkup extension tool, and are considering integrating it into company products. To stay safe, it's a good idea to use a password manager, which can let you store unique, complex passwords for your different web accounts. Google offers a free one with its user accounts.

About Our Expert

Michael Kan

Michael Kan

Principal Reporter

My Experience

I've been a journalist for over 15 years. I got my start as a schools and cities reporter in Kansas City and joined PCMag in 2017, where I cover satellite internet services, cybersecurity, PC hardware, and more. I'm currently based in San Francisco, but previously spent over five years in China, covering the country's technology sector.

Since 2020, I've covered the launch and explosive growth of SpaceX's Starlink satellite internet service, writing 600+ stories on availability and feature launches, but also the regulatory battles over the expansion of satellite constellations, fights with rival providers like AST SpaceMobile and Amazon, and the effort to expand into satellite-based mobile service. I've combed through FCC filings for the latest news and driven to remote corners of California to test Starlink's cellular service.

I also cover cyber threats, from ransomware gangs to the emergence of AI-based malware. In 2024 and 2025, the FTC forced Avast to pay consumers $16.5 million for secretly harvesting and selling their personal information to third-party clients, as revealed in my joint investigation with Motherboard.

I also cover the PC graphics card market. Pandemic-era shortages led me to camp out in front of a Best Buy to get an RTX 3000. I'm now following how the AI-driven memory shortage is impacting the entire consumer electronics market. I'm always eager to learn more, so please jump in the comments with feedback and send me tips.

The Best Tech I've Had:

  • My first video game console: a Nintendo Famicom
  • I loved my Sega Saturn despite PlayStation's popularity.
  • The iPod Video I received as a gift in college
  • Xbox 360 FTW
  • The Galaxy Nexus was the first smartphone I was proud to own.
  • The PC desktop I built in 2013, which still works to this day.

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