In April 2025, the threat intelligence firm Synthient compiled and disclosed a dataset containing approximately 2 billion unique email addresses and 1.3 billion unique passwords sourced from credential-stuffing lists circulating across underground forums. Unlike a traditional breach of a single organisation, this dataset represents the aggregated remnants of hundreds of earlier breaches — compiled into one searchable collection by attackers for use in automated account-takeover attempts. Synthient worked with the security community to make the data queryable so affected users could identify their own exposure.
Quick answer — was Synthient Credential Stuffing Threat Data breached?
Yes. Synthient Credential Stuffing Threat Data was breached in April 2025, exposing 1,957,476,021 records including email addresses, passwords. This breach has been independently verified. If your email was involved, your data may still be at risk today. Check if you were affected.
What happened in the Synthient Credential Stuffing Threat Data data breach?
In April 2025, the threat intelligence firm Synthient compiled and disclosed a dataset containing approximately 2 billion unique email addresses and 1.3 billion unique passwords sourced from credential-stuffing lists circulating across underground forums. Unlike a traditional breach of a single organisation, this dataset represents the aggregated remnants of hundreds of earlier breaches — compiled into one searchable collection by attackers for use in automated account-takeover attempts. Synthient worked with the security community to make the data queryable so affected users could identify their own exposure.
Because the dataset is drawn from prior breaches, any email appearing in it has already been tested against multiple services by automated tools. The 1.3 billion password entries include literal account credentials — meaning users who have not updated their passwords since their original source breach face active account-takeover risk today. Accounts at email providers, financial services, and subscription platforms are the primary targets for credential-stuffing automation.
At approximately 2 billion records, this is one of the largest collections of active credential pairs ever disclosed to the public in a single dataset. The scale reflects years of accumulated breach data being weaponised across interconnected criminal markets.
Learn more about what a data breach means for you.
Why was the Synthient Credential Stuffing Threat Data breach so dangerous?
Because the dataset is drawn from prior breaches, any email appearing in it has already been tested against multiple services by automated tools. The 1.3 billion password entries include literal account credentials — meaning users who have not updated their passwords since their original source breach face active account-takeover risk today. Accounts at email providers, financial services, and subscription platforms are the primary targets for credential-stuffing automation.
What data was stolen in the Synthient Credential Stuffing Threat Data breach?
Email addresses Passwords
Email addresses — used for phishing attacks and credential stuffing against your other accounts
Passwords — can be used to access your accounts directly or cracked to reveal your actual password
Timeline of the Synthient Credential Stuffing Threat Data breach
2020–2024
Credential-stuffing lists compiled from hundreds of earlier breaches and traded on underground forums
Early 2025
Synthient aggregates, deduplicates, and analyses the full dataset — approximately 2B unique emails, 1.3B unique passwords
April 2025
Dataset disclosed to the security community; records added to public breach database
April 2025
Affected users notified; records searchable by email
Is the Synthient Credential Stuffing Threat Data breach still dangerous in 2026?
Yes. Stolen data from the Synthient Credential Stuffing Threat Data breach remains dangerous years after the incident. Attackers routinely compile data from multiple breaches to build complete profiles, and credentials from 2025 are still actively used in automated attacks today.
Personal information like email addresses, phone numbers, and dates of birth does not expire. Even if you changed your Synthient Credential Stuffing Threat Data password, the other exposed data can be combined with information from other breaches to target you.
Learn how long stolen data stays dangerous.
What to do if your email was in the Synthient Credential Stuffing Threat Data breach
1
Change your Synthient Credential Stuffing Threat Data password immediately
Log into Synthient Credential Stuffing Threat Data and change your password to something strong and unique — one you have never used anywhere else.
2
Change any account sharing that password
If you reused this password elsewhere, change it on every affected account. Attackers test stolen credentials against hundreds of popular sites within hours.
3
Enable two-factor authentication
Turn on 2FA on Synthient Credential Stuffing Threat Data and every important account. Even if your password is known, attackers cannot access the account without the second factor.
4
Check your other accounts for this breach
Run a full email scan to see every breach your address appears in — not just this one.
Frequently asked about the Synthient Credential Stuffing Threat Data breach
What is the Synthient Credential Stuffing Threat Data breach?
It is a 2025 disclosure of a dataset compiled by the threat intelligence firm Synthient, containing approximately 2 billion unique email addresses and 1.3 billion passwords sourced from credential-stuffing lists that had been circulating on criminal forums.
Does being in this dataset mean my account was directly hacked?
Not necessarily. Your credentials appeared in this dataset because they were included in one or more earlier breaches. However, it does mean your email and password combination has been in active use by attackers for credential-stuffing attacks against other services.
Which service was breached?
No single service was breached. The Synthient dataset is a compilation of credentials gathered from many different prior breaches. The value to attackers was the aggregation and deduplication across hundreds of sources.
What should I do if my email appears in this dataset?
Change your password on every service where you used the exposed password combination. Enable two-factor authentication on your email provider, financial accounts, and any service storing sensitive personal data. Use a unique password for every service going forward.
Is this breach still dangerous in 2026?
Yes. The passwords in this dataset were compiled precisely because they were still actively used across multiple services. Any password you have not changed since it first appeared in a breach remains a working key for any account that shares it.
How this breach page is reviewed
Breach pages are built from structured breach records and reviewed for practical risk guidance by EmailLeaked. Risk labels reflect exposed data types and are intended to help readers prioritise action.