Analysts Flag the 20k UK Combolist and Its 20,159 Accounts

On March 23, 2023, HEROIC analysts flagged a combolist file named "20k UK" circulating on Telegram. The file contained 20,159 records, each pairing an email address with a plaintext password and the URL the credentials were tied to. Why This Is Dangerous: With more than 20,000 records and passwords stored in plaintext, this file gives an attacker a large, ready-to-use set of working login combinations that can be fed directly into automated tools with no cracking or decryption needed. What Was Exposed: The file contains email addresses, plaintext passwords, and the URLs each login was tied to. Why This Matters: A file of this size is large enough to be attractive for credential stuffing campaigns targeting UK-based banks, retailers, and government services. If any of these 20,159 people reused their password on another account, that account becomes vulnerable to takeover, identity theft, or financial fraud. How This Combolist Was Likely Built: Country-labeled combolists like "20k UK" are usually assembled by filtering a larger set of breached credentials down to accounts and email domains associated with that country, then packaged for distribution on Telegram to buyers who want regional targets. Check If You're Affected: If you live in the UK or hold accounts there, or reuse passwords across multiple sites, HEROIC's free breach scanner searches more than 400 billion leaked records so you can see if you're included and secure your accounts.