Synthient Credential Stuffing Threat Data Data Breach

What happened

During 2025, the threat-intelligence firm Synthient aggregated 2 billion unique email addresses disclosed in credential-stuffing lists found across multiple malicious internet sources. Comprised of email addresses and passwords from previous data breaches, these lists are used by attackers to compromise other, unrelated accounts of victims who have reused their passwords. The data also included 1.3 billion unique passwords, which are now searchable in Pwned Passwords. Working to turn breached data into awareness, Synthient partnered with HIBP to help victims of cybercrime understand their exposure.

Exposed data

Recommended actions

• Change your Synthient Credential Stuffing Threat Data password immediately, and update it anywhere you reused the same password.
• Enable two-factor authentication on the affected account and on your critical services (email, banking).
• Watch for targeted phishing emails referencing Synthient Credential Stuffing Threat Data — attackers weaponise breach data quickly.
• Check whether your email address appears in this breach on haveibeenpwned.com.