A massive leak of 183 million email passwords – including millions linked to Gmail accounts – was discovered online in October 2025, making it one of the largest credential dumps ever uncovered. The breach was not a direct hack of Google or Gmail itself; rather, the stolen credentials came from malware-infected devices (known as “infostealer” malware), which covertly extracted email addresses, passwords, and associated URLs from users’ personal computers and browsers.
The exposed dataset, called “Synthient Stealer Log Threat Data,” was gathered from underground channels – including Telegram groups and illicit online marketplaces – where cybercriminals share stolen credentials.
The dataset includes more than 183 million email-address-and-password matches. Around 16.4 million accounts were found to have never appeared in any prior breaches.
Many passwords were found in plaintext, heightening risks for users who reuse passwords across services.
While Gmail was not directly breached, credential stuffing attacks (using repeated password attempts) could compromise many accounts if reused logins remain active.
Google has firmly denied reports of any breach of its servers and emphasized that the only leaked data were those stolen through malware on users’ devices, not due to a vulnerability in Google’s technology.
Google recommends enabling two-step verification and using passkeys for added protection.
How to Check If You’re Affected
• Users can check whether their email address and password were involved by visiting HaveIBeenPwned.com and entering their email address. The site will indicate whether your credentials have been exposed in this breach or any previous incidents.
Security experts strongly advise updating passwords, using a password manager, and enabling multi-factor authentication wherever possible.
If reusing passwords for multiple services, it is essential to change them immediately to prevent further compromises.
What To Do Now
Use Have I Been Pwned or similar tools to verify exposure.
Change your affected passwords immediately.
Turn on two-step verification for crucial accounts (like Gmail, Outlook, Yahoo).
Avoid reusing passwords, and use a reputable password manager to generate unique credentials for every service.
This leak illustrates the ongoing threat posed by malware, especially infostealers, and the importance of implementing strong, unique passwords and multi-factor security measures for all online accounts.
